I'm on my GF's computer, she shows me how more frequently than not, the computer almost freezes up on her. Everything goes extremely slow, where it will take 3 or 4 minutes to refresh the desktop. After lookinginto things, I see the processor goes up to 100% ,and often stays there, with the only active processes being Explorer and System Idel Process, and Task Manager. (Others using between 1 and 10% of CPU time, but standard stuff) Tried stopping most proceesses from starting, and deleted a few programs that might have been corrupted (It ALWAYS started when opening WMP9, deleted that, for example). The system seems to run OK now, but I see it's still hitting 100% when opening most programs, or doing much of anything. It doesn't stay there any more and freeze the computer, but none of my other computers hit 100% often at all, and if they do, it'w when opening or processing huge files. This one will hit it for 3 or 4 seconds each time, and peak there every time I open calc.exe, for example. The RAM seems to work fine, any ideas?

It sounds like you GF computer has a memory leak somewhere, sometimes it's a sofware issue and sometimes it's a hardware issue. Here what I would do, back all her data files a just wipe the the machine and do a freah reload, if it's still happening then you have a Hardware issue...