Cool Web Search - installed itself in the background, took over everything, I think it modified the Windows kernel. Spent 3 months deleting registry entries (which immediately came back), files, programs, processes. running Hijack This! (not sure if it helped much, but I liked the name...
, going to Computer Cops, yada, yada, yada. Finally had to back off all the data and reformat the mofo....sigh...