After installing Windows 7, CHKDSK has ruined my Windows 10 HDD

Question

Pretty much the title.

I installed Windows 7 Ultimate the other day, after getting bored with Windows 10. I installed Win 7 on a 465 GB HDD, while Win 10 was on a 232 GB HDD, label D:\ .

After Windows 7 rebooted, it ran a CHKDSK and before I could skip it (I wan't paying attention, :/) it ran a CHKDSK on drive D:\ and found 'invalid security ID's.' It took maybe 1/2 hr to complete, and all seemed fine from the Windows 7 POV...

But then I rebooted into 10.

And I couldn't access anything. As soon as I logged in, I got pop-ups saying 'This couldn't be accessed' like Desktop, for example. Every single shortcut wasn't functioning properly, and settings (eg. personalisation) would say 'This doesn't exsist' or something like that.

I saw when it was running CHKDSK it was 'replacing' invalid security ID's with 'deafult' ID's. Would this be a problem?

I then also found out I could copy & paste stuff from drive to drive, but a problem was when I tried to run Steam on 7, as I had Steam linked up to my games on my 2nd drive, it would say 'Disk read error' when trying to start a game from my 10 drive. I was able to copy the 'steam' folder from the Win 10 drive, so I was still able to play CS from Windows 7. I just thought that might be helpful.

BTW, if you were somewhat confused, when I say 7 I mean my Windows 7 drive, and 10 my Windows 10 drive.

Sorry for the long explenation, I just had a lot of things to get out.

Thanks in advance!

horIzoN.

Edit: It has just been pointed out to me that I'm not asking what I want to happen next. I want to fix these 'permissions' errors and get Windows 10 working. Also, just to see if I missed anything, I notced the error also says 'Access is denied' when I just booted into Windows 10. The 'Start Menu' will never pop up as well. I am a full admin.

Solution

One source of the problem is Fast Startup in Windows 10, which is basically a logoff + hibernation.

Windows 7 was unable to recognize that state of the Windows 10 hard disk, so it just proceeded to destroy it. Then Windows 10 booted and completed the destruction.

Anyone thinking of dual-booting Windows 7 and 10, should first Turn Off Fast Startup in Windows 10. Or else. Even then, one might encounter a situation where each Windows version will demand on each reboot to chkdsk the disk of the other version, which is of course risky.

Another problem was using incompatible user accounts, since any account created by one operating system does not exist in the other, therefore doing chkdsk with one version on files modified by the other is playing hell with the security IDs of the files.

The "solution" for the accounts incompatibility problem is to use only standard user accounts. A standard account that might be safe to work under is the hidden built-in elevated Administrator account, which needs to be enabled. However, Microsoft has good reasons for hiding that account, mostly for security.

If you do not have a prior disk-image of the Windows 10 disk, the situation is pretty grim. The only measure which might return some sanity to the Windows 10 installation is probably Repair Install Windows 10 with an In-place Upgrade. If this does not work, then a full reinstall is required, after formatting the disk.

Dual-booting these two versions of Windows is inherently a risky proposition. A safer solution would be to use Hyper-V under Windows 10 to create a virtual machine with Windows 7 installed. This would be much safer than dual-boot.

Comments

[maxbc]

Have you tried running CHKDSK manually from Windows 10? What does it say? Looks like Windows 7 is confused by the presence of Windows 10 (normally it should just act as if it was not there, or just a data drive). Have you followed a guide to successfully dual booting 7/10?

[horIzoN]

I'll try the CHKDSK on Windows 10, and on my old PC I was able to successfully dual-boot, and it never did a CHKDSK. I don't think it <bold>detects Windows 10, it just verifys the files, and then it replaced the 'security ID's'; I belive that has something to do with permissions.

[horIzoN]

I've just done a CHKDSK on 10; it thought everything was fine, no errors at all. I don't know how you fix this... it's really starting to annoy me.

[Andrew Morton]

If you'd taken backups it might be easier. There is plenty to shout "why not?" at in How do I restore security settings to a known working state? Any chance of copying your data off the drive and re-installing/refreshing Windows 10?

[horIzoN]

After seeing this, I did copy my Steam folder and a bunch of documents that I did need. I'm gonna go through my data now, and then see what I can do next.

[Dmitriy]

Oh, so having Windows 7 and Windows 10 on the same HDD is not a good idea? I was wondering why Windows 7 is always trying to do chkdsk after booting in Win 10.

[harrymc]

@Dmitriy: Not a good idea, unless you stay within the above draconian limitations. And in any case, don't ever do chkdsk in Windows 7. The best would be not to share disks between the two OS except as read-only.