Could this be related to the trojan problem you have???
You could try system restore via safe mode.
To get to safe mode, hold the F8 key just after switching on, select safe mode from the menu that appears, it gives you a very basic desktop display.
When logged in go to start, all programs, system tools and system restore, follow the prompts to 'roll back' the PC to a few days ago or any relevant checkpoint on the list, it will then reboot and should be good as when it was a few days ago.
However, things can go wrong when messing with this stuff, hope you have your files backed up.
The problem is, whatever caused it could reoccur, either a virus or a dodgy system update from microsoft, but restore could get you out of the poop for now.