Windows 8 won't boot in Normal or Safe Mode

I made a backup of the registry before doing the MarkC Windows 8 mouse acceleration fix, did the fix and I felt the mouse was really weird so I tried to backup the registry using the backup I made beforehand, Windows 8 being its usual self, denied access even though I ran it as an Administrator, then explorer.exe wouldn't run and nothing would open, I rebooted and now I get a black screen. Windows 7 on the same pc in dual boot works fine, I tried using startup repair and system restore but it says they are not compatible with this version of windows, it's windows 8, what's the problem here?
Is there any way I can load the backup registry from windows 7 for windows 8?
I can use the repair screen CMD, I tried some repair commands, they said successful except the bootrec /rebuildbcd one, (I think it was that one) that said it detected 0 Operating Systems.
How can I save Windows 8? I can't download GTA 5 again at its 50kbps speed that rockstar servers seem to do.
Thanks in advance.
 
Solution
You cannot use a Windows 7 registry backup for Windows 8. That will never work.

Sounds like you have a corrupt installation or faulty boot record. Possibly multiple boot records or a boot record from a prior version of windows that still has a partition on the drive. I'd reinstall using the clean method outlined at the following link and be sure to delete all the existing partitions aside from the factory recovery partition if there is one. If you have physical installation media, just delete all partitions on the target drive.

http://www.eightforums.com/tutorials/2299-clean-install-windows-8-a.html
You cannot use a Windows 7 registry backup for Windows 8. That will never work.

Sounds like you have a corrupt installation or faulty boot record. Possibly multiple boot records or a boot record from a prior version of windows that still has a partition on the drive. I'd reinstall using the clean method outlined at the following link and be sure to delete all the existing partitions aside from the factory recovery partition if there is one. If you have physical installation media, just delete all partitions on the target drive.

http://www.eightforums.com/tutorials/2299-clean-install-windows-8-a.html
 
Solution


It is a windows 8 registry backup, but I am asking if I can install it to windows 8 from windows 7?