Unable to boot into Windows 10 following restart after an Itunes update on my Toshiba Satellite

[NewtonsCrouton]

I made the idiotic mistake of deciding that tonight was the night that I install an iTunes update that I've been putting off for a couple days, even though I have an exam tomorrow morning and NEED my laptop. I believe the update was version 12.3.1, since that is the newest on their website.

Anyways, it prompted me to restart my laptop after install, and upon starting up I found that my laptop couldn't boot into Windows. It would simply go to a blue screen with a frowny face that said it was attempting to perform system repair. The repair would finish and after it went straight back into a second repair. After a couple of these, it informed me that I could do a system restore, which I tried, but that resulted in my laptop restarting and being stuck at the Toshiba boot screen.

After waiting a long enough time at that screen, it finally got to another blue screen saying that restore wasn't working, but I could use the system repair options. I tried to go into safe mode from there, but Windows still wouldn't boot and I just had to go through the same loop above to get back to system repair options. This time, tried just using the command prompt option so I could back up my files, which is where I'm currently at.

I should note that I've been having problems with Windows 10 since a recent build that happened about a week ago. Besides just making my startup really slow and having "System" take up a crapton of memory in task manager all the time, Explorer.exe would crash about every other time I opened a file from the file explorer

Any help would be so extremely appreciated, I have no idea what I'm doing here and I really need access to this laptop tonight at whatever cost. I haven't made a recovery drive for Windows 10 (I updated from the Insider Preview and completely forgot to), but I do have my recovery drive for the original Windows 8.1 OS that I made right after getting the computer.

Make: Toshiba Satellite
Model: E45-B4100
OS: Windows 10 Build 10565 (Insider Preview)

Supplemental Questions
1) My external hard drive is still currently attached to my laptop, but I'm scared to just pull it out. Is there a way to eject, without having to turn my computer off and go through the same time-consuming loop again, from command prompt? Or is it relatively safe to just pull it?
2) I downloaded a Windows 10 iso from my girlfriend's laptop and was going to try to make a recovery drive on a USB to use the repair options in there. Is that a good idea? I got it from here http://www.microsoft.com/en-us/software-download/techbench
3) I was informed after a couple of the initial system repair things that there was a log file at C:\Windows\System32\Logfiles\Srt\SrtTrail.txt. Can I use this to help em figure out what's wrong, or would it be useful to anyone to help me out?
4) In command prompt, I want to try uninstalling iTunes because I just figure that it's the source of my problems. Is that a good idea? If so, how can I do this?

Huge thanks to anyone who can help me at all

EDIT: I believe the build is 10565

 

[harryfishrules]

First of all, I hope your exam went well. As far as your external HDD goes, it should be safe to remove it but to be sure, it's best to remove it when the PC is off to avoid any data corruption issues. As far as the log file and uninstalling iTunes go, we'll cross that bridge if we need to.

Here's some steps I'd like you to follow and see whether they help:

There's a Tom's Hardware video here: (http://www.tomshardware.co.uk/faq/id-2569556/safe-mode-windows.html) that shows how to access safe mode a second way (it's the second demonstration in the video).

You'll need a Windows Installation CD/USB to do this, you can create one using the tool here: (http://windows.microsoft.com/en-gb/windows-10/media-creation-tool-install)

If this gets you to the Safe Mode login screen, login as usual.

If it does login correctly, follow these steps:

1. Press "Windows + X" at the same time
2. Select “Command Prompt (Admin)”
3. Accept any User Account Control popup for “Windows Command Processor”
4. Enter "sfc /scannow" (without the speech marks) into Command Prompt followed by enter
5. Let the scan complete fully

6. Reboot and attempt to boot to the standard desktop
7. If this fails, follow the video again to get back into safe mode. If however, it works, then follow the first part of the video to get into safe mode the "normal" way.

6. Press "Windows + R" at the same time
7. Enter "control wuaucpl.cpl" (without speech marks) followed by enter
8. Windows Update should open
9. Select "Scan for Updates"
10. Install all updates including optional ones

All the best and let me know how it goes.