My parents desktop was running very slowly so I did a virus scan and came up with 4000+ files all infected with the same virus I-Worm.Netsky.C. Almost 90% of the infected files were in C:\Program Files\Common Files\Microsoft Shared and the rest were in Yahoo Mesenger folder in Documents and Setting (don't remember the exact folder) and a few other were scattered around my drive. I have absolutely no idea how 4000+ virii got on the computer since I'm pretty sure my parents don't open strange attachments, plus I did a fresh intall of Windows XP Pro two weeks ago. I also have Zone Alarm and AVG running. Anyone have any ideas as to how this happened?