*EDITED*
This is an update to what I posted. Apparently everything I did was wrong. There's a much more simple solution which can be found here:
http://technet.microsoft.com/en-us/library/dn336946.aspx (Thank you to darkbreeze for providing the link)
And a utility for converting MBR to GPT can be found here:
http://www.partitionwizard.com/free-partition-manager.html (Thank you to Hawkeye22 for providing this link)
*ORIGINAL POST - (don't bother reading, not really relevant and makes me look like a total newb....)
I came across this problem after building a new desktop recently. But actually, I'm posting more of a solution, than just the problem...
My old system was a Windows 7 laptop, with 4 external USB hard drives connected to it. 3 of these drives were formatted using NTFS, and MBR (Master Boot Record) but one of them was formatted with NTFS and GPT (GUID Partition Table). At the time, I didn't know it... but this is a VERY significant point which I will explain in a bit. (GPT vs MBR)
I built my new desktop with an SSD drive and installed Windows 8.1 on it. Then, I took the external drives out of their casings, and installed them into my desktop as internal drives, connected by SATA cables etc.
After I booted for the first time, and loaded windows, 3 of the drives showed up as unformatted, and only ONE drive didn't. Of course, it was the drive that was formatted with GPT that was working fine, and the MBR drives were all unrecognized by Windows 8.1. At the time, I didn't know that this was the problem though. So I did some research, and everyone said the same things. It's an NTFS issue, or the drives are corrupted, or whatever... all untrue... and I knew it. But I still didn't know what was causing the problem.
Unfortunately, I couldn't find any real information, but I did hear about a utility called testdisk. So I bought a new hard drive so I could have free space, and formatted... this is when I discovered the choice between MBR and GPT. When I installed the new unformatted drive, it asked me which partition table I wanted to use.... MBR, or GPT. That's when it hit me. So of course, I checked the three drives that were having trouble and discovered that they were all MBR, and the drive that worked fine was GPT.
So now I'm pretty sure that the problem is related to MBR vs GPT. Old MBR disks do not work with Windows 8.1. It sees them as unformatted. I actually connected the disks to the USB interfaces and reconnected them to the old laptop (Windows 7) and they all worked fine again. But when I put them back in the windows 8.1 desktop, they showed up as unformatted again.
So the most important message here is: YOUR DATA IS STILL THERE, so don't panic. And DON'T FORMAT THE DRIVE, ESPECIALLY A FULL FORMAT!
All you need to do is use a utility called testdisk, which can be found here:
http://www.cgsecurity.org/wiki/TestDisk
It's free, and there is documentation on how to use it on the testdisk website. It will allow you to access the files on the MBR disk, and copy them to another hard disk. If you don't have a working secondary hard disk in your PC, then you could be in trouble.
Basically, you will need a working hard drive in your system, so you have a place to copy your files using testdisk. After you copy the files off the MBR disk, you can then format the MBR disk as a GPT disk, and it will work fine. Then you can copy your files back to it.
As of yet, I haven't found any way to convert an MBR disk to GPT WITHOUT formatting, but if someone knows how to do it, please post it here. When you try to convert it using Computer Management, it will ask you to format first.
This is apparently an issue that Microsoft completely overlooked. They have no documention on it, and even their operating system sees MBR disks as just being "corrupted" or in their words exactly in the error message: "E:\ is inaccessible. The Volume does not contain a recognized file system. Please make sure that all the required file system drivers are loaded and that the volume is not corrupted."
The message is almost useless, and doesn't mention MBR or GPT. It does mention file system drivers, but that's confusing, because I associated file system with NTFS or FAT32 which are file systems that is NOT the issue.
Maybe there are some file system drivers that will allow Windows 8.1 to recognize older MBR disks... I don't know. Need someone who's a real expert to answer that one.
Hope this helps anyone out there having this issue...
This is an update to what I posted. Apparently everything I did was wrong. There's a much more simple solution which can be found here:
http://technet.microsoft.com/en-us/library/dn336946.aspx (Thank you to darkbreeze for providing the link)
And a utility for converting MBR to GPT can be found here:
http://www.partitionwizard.com/free-partition-manager.html (Thank you to Hawkeye22 for providing this link)
*ORIGINAL POST - (don't bother reading, not really relevant and makes me look like a total newb....)
I came across this problem after building a new desktop recently. But actually, I'm posting more of a solution, than just the problem...
My old system was a Windows 7 laptop, with 4 external USB hard drives connected to it. 3 of these drives were formatted using NTFS, and MBR (Master Boot Record) but one of them was formatted with NTFS and GPT (GUID Partition Table). At the time, I didn't know it... but this is a VERY significant point which I will explain in a bit. (GPT vs MBR)
I built my new desktop with an SSD drive and installed Windows 8.1 on it. Then, I took the external drives out of their casings, and installed them into my desktop as internal drives, connected by SATA cables etc.
After I booted for the first time, and loaded windows, 3 of the drives showed up as unformatted, and only ONE drive didn't. Of course, it was the drive that was formatted with GPT that was working fine, and the MBR drives were all unrecognized by Windows 8.1. At the time, I didn't know that this was the problem though. So I did some research, and everyone said the same things. It's an NTFS issue, or the drives are corrupted, or whatever... all untrue... and I knew it. But I still didn't know what was causing the problem.
Unfortunately, I couldn't find any real information, but I did hear about a utility called testdisk. So I bought a new hard drive so I could have free space, and formatted... this is when I discovered the choice between MBR and GPT. When I installed the new unformatted drive, it asked me which partition table I wanted to use.... MBR, or GPT. That's when it hit me. So of course, I checked the three drives that were having trouble and discovered that they were all MBR, and the drive that worked fine was GPT.
So now I'm pretty sure that the problem is related to MBR vs GPT. Old MBR disks do not work with Windows 8.1. It sees them as unformatted. I actually connected the disks to the USB interfaces and reconnected them to the old laptop (Windows 7) and they all worked fine again. But when I put them back in the windows 8.1 desktop, they showed up as unformatted again.
So the most important message here is: YOUR DATA IS STILL THERE, so don't panic. And DON'T FORMAT THE DRIVE, ESPECIALLY A FULL FORMAT!
All you need to do is use a utility called testdisk, which can be found here:
http://www.cgsecurity.org/wiki/TestDisk
It's free, and there is documentation on how to use it on the testdisk website. It will allow you to access the files on the MBR disk, and copy them to another hard disk. If you don't have a working secondary hard disk in your PC, then you could be in trouble.
Basically, you will need a working hard drive in your system, so you have a place to copy your files using testdisk. After you copy the files off the MBR disk, you can then format the MBR disk as a GPT disk, and it will work fine. Then you can copy your files back to it.
As of yet, I haven't found any way to convert an MBR disk to GPT WITHOUT formatting, but if someone knows how to do it, please post it here. When you try to convert it using Computer Management, it will ask you to format first.
This is apparently an issue that Microsoft completely overlooked. They have no documention on it, and even their operating system sees MBR disks as just being "corrupted" or in their words exactly in the error message: "E:\ is inaccessible. The Volume does not contain a recognized file system. Please make sure that all the required file system drivers are loaded and that the volume is not corrupted."
The message is almost useless, and doesn't mention MBR or GPT. It does mention file system drivers, but that's confusing, because I associated file system with NTFS or FAT32 which are file systems that is NOT the issue.
Maybe there are some file system drivers that will allow Windows 8.1 to recognize older MBR disks... I don't know. Need someone who's a real expert to answer that one.
Hope this helps anyone out there having this issue...