This is one I put together myself a few years ago. It has an Athlon 64 3200 processor, Western Digital 120 Gig HD, 768 meg of RAM.
It started as soon as I installed Nero 7. I uninstalled it, restarted and the "Common" folder went away..... when I reinstalled it, it came back. Sorry, I should have mentioned that in the first place.
I run a virus scan every day, and scan for spyware about once a month.