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.
Best Answer
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.