All Day Saturday Removing 62 (!!) Viruses From My Computer

Yep, 62. I use SpyBot for malware, and a friends' reco got Avast. Things seem to be working much better so far, but it freaks me out!! Where are these things coming from??(not to protest, but I really don't go to any sites that would download this stuff, or open iffy attachments)
After 8 hours yesterday tweaking the computer, I'm pretty sick of it.