ok, you're clear of a spyware or equivalent then.
and it doesn't sound like a low memory issue either.
Try running a defrag to align your files, it isn't a big help, but if a system is being picky for some reason it can help.
The fact that it happens while dealing with Windows files could be a big problem.
Try running 10 or 11 different programs, anything, small large, and see if you have any issues, that should be enough to push your RAM the same as an installer and should give some feedback on your RAM situation.