On my 11th attempt, I finally managed to run Norton's online virus scanner all the way without my computer crashing. Only one trojan, W32.HLLW.Chemsvy, from a file I downloaded the other day...after the onset of my computer problems. From what I've read, it's pretty benign, so I doubt it was the source of my problems.
I guess I'll have to look at software and hardware issues now.
Thanks for your help
