Don't know if this can help you, but go to Start > Help and Maintainance > Undo the changes done with "restaurate" System (dunno if that word exists). Then to create a point ... and you can there go back with dates to the last time your computer worked okay.
I had some problems like that, the file that was creating a conflict was the AIM, I had all the problems, like.. only one speaker would work, system crashes, so on. I had to reinstall Windows and don't d/l AIM anymore. (the tech guy told me that AIM makes that kind of problems with Windows XP).