[Saintly]

Try starting in safe mode.
when the bios screen appears (when you start your PC) press F8 repeatedly until you get a text menu with options on it (if windows starts to load you have missed it and will need to try again). select safe mode and the system will start with very basic options and drivers. any extra start items will not be started. in this mode you can re-install or un-install applications as needed, copy files to another disk drive or perform other tasks to try to fix it.
If you start it in safe mode and it stays up without re-booting then your problem is software and should be able to be fixed. would be good to connect another drive and copy your files to it if possible (just to be safe).