Windows 10 Black Screen With Flashing Underscore

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Jkoukal

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Jan 13, 2017
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Hi, so I was going to let my computer do a routine update that required restart overnight and by the time I go to check on it in the morning I'm greeted with a black screen that has a flashing underscore in the upper left corner of the screen that's about 2 lines down. It will load the bios splash art and let me go into the bios (in my case I have an MSI motherboard). And I have tried putting a windows installation media (USB) and loading that and choosing repair instead of install and I don't get the option to boot into safe mode (tried f8 and tried going through the advanced settings but the startup options isn't even an option). Tried startup repair but it said that it couldn't fix my problem, then tried to restore to a previous build and it wouldn't let me. I was able to navigate to the command prompt and notepad to see if my hard drive was picked up and it was, looked through and all my documents appeared to be there. I was able to pull what I needed/wanted on a small USB stick but I would like to not have to wipe my HD clean and start over. Any help is much appreciated. This is the end of 2 consecutive days of looking stuff up and a worthless phone call with windows support center, so any ideas are much appreciated. Thanks.
 

Colif

Win 10 Master
Moderator
NTFS = New Technology File System. Its what every version of windows used since XP - http://www.howtogeek.com/235596/whats-the-difference-between-fat32-exfat-and-ntfs/

Since you already have win 8 on PC it has GPT now, that is clear when error mentioned the EFI partition
File:\EFI\Microsoft\Boot\BCD
error code: 0xc000000f
As far as I know, all motherboards that have UEFI also support Legacy mainly as it lets them sell more of them, and because UEFI is backwards compatible.

Repair MBR - you are right but its like why people still say BIOS, MBR & BIOS have been used for last 26 years, it will take a while for people to change. Instead, rebuild bcd & rebuild MBR on Win 10 mean the same things, or should I say, the solution to both is the same.

GUID is probably like a MAC address (networking isn't one of my strong points). MBR only allowed you to boot from a limited range of device types, GUID lets you boot from devices that may not exist yet, as well as the usual network drives, It recognises the internet of things, so it could boot up off your fridge or remote control for house...

your error i quoted above also answers the bcd question. it exists in both MBR & GPT, been around since Vista - https://en.wikipedia.org/wiki/Windows_Vista_startup_process#Boot_Configuration_Data
 
The flashing underscore means that the motherboard is waiting for a bootable device because it hasn't detected that any bootable devices are connected. Is the boot sector on your HDD corrupted or incorrectly installed?
 

Jkoukal

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Jan 13, 2017
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I am giving this info because I feel like other people have different options under these screens so maybe me having different options means something else? but here it is.
I did this step by step (loading the installation media of windows 10 through thumb drive and using my bios to boot the usb),but when I select repair this computer (or whatever it says) instead of "Install now" I get 2 options:
Troubleshoot and turn off pc. (some people have a 3rd option) and under troubleshoot it has 6 options:
System Restore - doesn't work because there is no other restore point to load
System Image Recovery - haven't tried
Sartup Repair - doesn't work because it can't fix the problem
Command prompt
UEFI Firmware settings - this option strikes me as odd considering I have never seen others with it on this screen
Go back to previous build - I have tried this and theres no previous build. (guessing it's for a bad upgrade from 8.1 to 10)

but disregard all of that in case those menu options don't mean anything. I was able to go into command prompt and type the command : bootrec /rebuildbcd (It starts me off in drive X which is the "boot" drive (its the name boot not the drive in which my OS is on, but I'm guessing it might be a partition of my HDD)) so althought its not my OS drive i typed it in. It said it had found a windows installation on my Drive E (which makes sense when i go into notepad and view files its the drive with all my stuff and OS in it) and so i continue to type "y" for me wanting to add it to the boot list. And instead of saying: "The operation completed successfully" it said: "The requested system device cannot be found". So obviously something is up I hope this helps.

And this black screen started up after (I'm guessing a failed installation) a normal update of some kind. This wasn't me upgrading from 8.1 to 10 or anything but I have had it for awhile and just a normal update and after it restarted my computer it started this.
 

Jkoukal

Commendable
Jan 13, 2017
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not sure how to check but look at the response to colifs suggestion to see if that helps.
 

Jkoukal

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Jan 13, 2017
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UPDATE: so this morning I go to try to fiddle with my computer and then I go to the bios and load up the installation media I have so I can go to the command prompt and upon loading up the media which normally goes to the language selection and what not, it instead goes to this blue screen saying my BCD is missing or is corrupted. I would try to post the picture but I don't see an attachment button....-_-
but it says:

Recovery

Your PC/Device needs to be repaired

The Boot Configuraion Data for your PC is missing or contains errors.

File:\EFI\Microsoft\Boot\BCD
error code: 0xc000000f

You'll need to use recovery tools. If you don't have an installation media (like a disc or USB
device), contact your PC administrator or PC/Device manufacturer.

Press Esc for UEFI Firmware Settings

when I push Esc button it seems to restart the computer then it goes into the bios and then I don't really know what UEFI setting to really change or where to go from here. Just kinda curious as to why it suddenly wont boot the Media stick and goes to that screen instead.
 

Colif

Win 10 Master
Moderator
I can't say I have seen it have a BCD error booting off USB stick before, I mean, it should be running off the stick, not looking for the efi file? Did you set USB as 1st boot? what is 2nd choice in boot order?

BCD = Boot Config Data, its the file that the PC looks for to boot windows 10, the command I gave is meant to fix the exact error you just got... As far as I know the USB stick shouldn't care if its there or not, as installer can run on blank hdd, so makes me think its trying to boot hdd instead
 

Jkoukal

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Jan 13, 2017
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Yea I'm trying to reset the USB drive and create another media to boot from but when I boot up my computer instead of going to the bios I go into my boot settings (which is f11 for me) and I select my USB drive so it wants to load that up because if it were to load my HDD it would just go to that black screen. I'm going to try and repair the MBR and the BCD and see if that helps but other than this what do you think about the reply to your first post Colif?
 

Colif

Win 10 Master
Moderator
which reply? ko888 is suggesting the same thing as the bcdedit function I suggested.

The boot sector of your hdd is called the EFI partition. The BCD is inside that partition and the fix should repair the bcd so your Windows Boot Manager, which should be 1st item in a normal boot order (if you not booting off USB) will find the right file to boot off and you shouldn't get this error.
 

Jkoukal

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Jan 13, 2017
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Well before the whole USB stick thing this morning (which I'm making a fresh one) when I tried to use the command: "bootrec /rebuildbcd" it showed the partition of my HDD that had windows and when I wanted to add it to the boot list it said that "the requested system device cannot be found"
 

Jkoukal

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Jan 13, 2017
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Ok first off, using that new windows media worked just fine going into the command prompt this time don't know what happened, and second, I started off with the commands bootrec /scanos, which found my OS on my E drive, then with bootrec /fixmbr "operation completed successfully" then bootrec /fixboot, same thing, then rebuildbcd which turned out the same thing as before. Now when I go to do chkdsk /f it says "the type of the file system is NTFS. Cannot lock the current drive. Windows cannot run disk checking on this volume because it is write protected". So now I go to do chkdsk /r and the same thing. Should I be running this on my X drive which doesn't contain my system files or OS? or run it on my E drive that has windows on it?
 

Jkoukal

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If i do diskpart and list my volumes it gives me these options:
volume ### LTR LABEL Fs Type Size Status info
volume 0 G dvd-rom 0 MB no media
volume 1 C system rese NTFS partition 350 MB Healthy
volume 2 E NTFS partition 930 GB Healthy
volume 3 F NTFS partition 450 MB Healthy Hidden
Volume 4 D USB FAT32 removeable 7526 MB Healthy
 

Colif

Win 10 Master
Moderator
I don't see a drive X in diskpart so its likely a ram drive set up by the installer to run itself in.

C drive shouldn't be 350mb, that is the size of the System partition - The EFI System partition that contains the NTLDR, HAL, Boot.txt, and other files that are needed to boot the system, such as drivers.
E drive should be C drive as its the 930gb partition win 10 is in
F is MSR - The Microsoft Reserved (MSR) partition that reserves space on each disk drive for subsequent use by operating system software.
D is obviously your USB stick

It has to be mentioned that the USB drive does mess with drive letters so my confusion might not be a problem (think I need a 2nd option)
 

Jkoukal

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do you think maybe trying to mount the Boot X: drive to the HDD? when I go into notepad and click open under file, I can see all of the drives and X is on there. So maybe since my computer doesn't see that Boot is on my HDD it stops where its at hence the black screen?
 

Colif

Win 10 Master
Moderator
i don't know what is going on, it seems to me that C & E drives have swapped labels and that is likely the reason PC isn't booting now,

The way UEFI boots is by looking for a particular file on the EFI partition and that file probably has a hard coded file path to the loader for windows.
As far as I know the 1st step doesn't look for drive letters so it should be finding volume 1 but the 2nd step, the file name, might have C: as the drive location and it would be going nowhere as C is not the drive it is expecting to find.

I don't know how C & E got mixed up... volume 1 shouldn't even have a drive letter, nor should F - I don't use diskpart a lot so it might allocate them
 

Colif

Win 10 Master
Moderator
Here is what my C drive looks like in diskpart, no extra drive letters



the free space must mean unallocated as i would have noticed if I only had over 2mb of free space on all my drives.
 

Jkoukal

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Jan 13, 2017
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Well I could try swapping the volume names of the partitions. because as far as I was concerned I swore that C was my main drive as well, whenever I would go through my file explorer on a normal basis, but then again like you said I have no idea why they would switch or how. Because worse case scenario if it doesn't work I could just swap the letters back to how they originally were without repercussion??
 

Jkoukal

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Jan 13, 2017
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That's weird. I'll take a picture of my command prompt and post it on here so it's easier on the eyes instead of me typing it. How do you attach images to the post?
 

Jkoukal

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Jan 13, 2017
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maybe yours looks different since it looks like you have 2 disks. the 1 is the SSD that presumable has your os on it and what not then the second being a 2 tb HDD? so maybe that second drive will have multiple partitions and letters?
 

Colif

Win 10 Master
Moderator
I wouldn't swap them as I doubt its that easy

You might have to fresh install to fix it. Before you do that though, I would try thing and copy anything off PC you want to rescue: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/

once you backed it all up, use the installer you have and follow this guide to do a clean install: https://www.tenforums.com/tutorials/1950-windows-10-clean-install.html

Did you originally upgrade from win 7 as your partition number makes me think you did. If so, win 10 will want you to delete all the partitions on hdd before it will install on it. A normal win 10 install has 4 partitions, you have 3 of them...

Partition 1 - Recovery
Partition 2 - System - The EFI System partition that contains the NTLDR, HAL, Boot.txt, and other files that are needed to boot the system, such as drivers.
Partition 3 - MSR - The Microsoft Reserved (MSR) partition that reserves space on each disk drive for subsequent use by operating system software.
Partition 4 - Primary - Where Windows is to be installed to.
but I have no idea what the 4th does anyway.
 

Colif

Win 10 Master
Moderator
I was showing you the detail and my ssd isn't exactly right anyway as I only have 2 partitions on Drive 0, not the 4 I should have. It was more to show you my 450mb partition has no drive letter

My ssd was result of me messing up my install, and hdd does have 2 partitions but neither involved with win 10, as you can see



easiest way to attach screen shots is click on the post an answer button and use the icon next to the A above the text box to type in the link to the photo and the forums will add the necessary tags
 
When I did a clean install of Windows 10 on a new Samsung 850 EVO 500GB SSD this is the partition list:

C++:
DISKPART> detail disk

Samsung SSD 850 EVO 500GB
Disk ID: {1318DE3A-D3CB-4FC0-9805-4556A7D89B09}
Type   : SATA
Status : Online
Path   : 0
Target : 0
LUN ID : 0
Location Path : PCIROOT(0)#PCI(1F02)#ATA(C00T00L00)
Current Read-only State : No
Read-only  : No
Boot Disk  : Yes
Pagefile Disk  : Yes
Hibernation File Disk  : No
Crashdump Disk  : Yes
Clustered Disk  : No

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 0     C   Samsung850E  NTFS   Partition    465 GB  Healthy    Boot
  Volume 1         Recovery     NTFS   Partition    450 MB  Healthy    Hidden
  Volume 2                      FAT32  Partition    100 MB  Healthy    System

DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    Reserved           128 MB    17 KB
  Partition 2    Recovery           450 MB   129 MB
  Partition 3    System             100 MB   579 MB
  Partition 4    Primary            465 GB   679 MB
Partition 1 is the MSR Partition and doesn't show up in the Disk Management tool.
Partition 2 is the Recovery Partition
Partition 3 is the EFI System Partition
Partition 4 is where the Windows 10 OS and Applications are installed
 

Colif

Win 10 Master
Moderator
When i fresh installed i didn't know what GPT was before i started and panicked when i was told win 10 wouldn't install on the drive it had literally just been on, so I deleted all the partitions and not knowing what to do next, turned PC off and sat around wondering what to do. I decided to try again and on this 2nd attempt win 10 probably did create 4 partitions like yours has but i didn't know it was meant to, and deleted all and created 1 232 gb partition and win 10 accepted it as it was in GPT format by that stage.

So I have 2 partitions now only as 1 of the Win 10 version upgrades decided I needed it. The 232gb partition does everything the 2 missing ones should do. Next time i clean install I will know better.
 

Jkoukal

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Jan 13, 2017
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yea I figure this was the first PC I built so I was bound to make some mistakes and loading the OS was probably one of them being a noob a couple years back. But i suppose learning has a curve. I'm pretty sure I started with windows 8.1 pro then a couple months later I updated to 10 when it came out. I'm sure when I installed the OS I messed something up and it was just a matter of time before some update broke the structural integrity of my OS. But I've accepted that I'll have to backup everything and clean install, not too mad though considering I'll have a sturdy foundation for later on so oh well. I'm curious though, so on the SSD I'm sure you have windows installed and that makes it a faster machine, and then on your 2tb HDD you have all your personal documents and programs and what not so if this were to happen in your case would you be able to just clean install on your SSD and not have to worry about it affecting any of your vital other documents on the HDD? (curious because I remember debating whether or not I should do a split like that when I first built my computer but my budget restricted me a bit so I held back, might consider that an option)


BTW: what does GPT mean or NTFC or EFI or UEFI and what not. I've never had to mess with partitions (let alone the fact they existed) and the whole boot and OS setup and how it works so any info you may have for me would be nice. Messing with computers is fun for me (as long as I can fix the problem....-_-) and anything extra I could learn from this would be nice.
 
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