I know this is going to sound stupid, but due to a faulty RAM module, my Windows 7 x64 crashed with a blue screen, and after reboot, my theme was lost. Sadly, I can't seem to figure out how to get it back: it seems to me that Aero is disabled, but switching to an Aero theme doesn't change the horrible appearance of my windowing system.
I tried to use the system restoration tool, but it failed - and now it seems that I don't have any valid restoration points either.
This is what my theme looks like:
If anyone has a clue about what's going on with this computer, it'd be much appreciated.