PC error Help! :(

[Ishi]

OK, I have Windows Vista Home Premium 32 Bit on dual core Intel Processors and 1 GB RAM but now my computer won't start!!!

 

It would start, I can see the green loading bar but when it comes to the part where I have to log in, I can't see the log on screen. I can see the white cursor but around it was pure black screen

 

This is how the problem might have started:

 

I saw the close button on some of the dialog boxes won't work so I restored a backup of one particular registry key. I restored a backup of the whole HKey-CLASSES- ROOT-CLSID key to be exact.I had to restart the computer for the changes to take effect but I forgot to close MS Office Groove so I had to close that before shutting down, but during the shutdown process, I can't see the blue-green log off screen, it was pure black, I can only see the cursor so I did a manual restart anyway.

 

When I rebooted the computer, it won't even open. I can still get to the point where I see the green loading bar. But It won't display the log on screen for me to log in. I can only see the cursor but it was around a pure black screen. Since I couldn't even open it, System Restore is not an option. When I rebooted it again, I can't see the Last Known Good Configuration option anyway. Same thing would happen even if I start in safe mode. Can't tell if it was a physical damage on my computer or if it was a virus but it only happened after I restored a backup of one registry key that was potentially the cause. Perhaps it was a virus or perhaps it could have been my mistake to restore that backup. Opinions and help on this one please???