After reformat, old program files?

[sebluver]

I recently reformatted my computer (long spell during which I had no internet, it got fixed and all is dandy now). I had the default "free 6 months of AOL" set up on the computer, so I went to the install/uninstall programs place and uninstalled it. The programs installed in there were the normal ones that should be in there after a reformat, it was basically empty.

Now comes the weird part. McAfee recommended running a virus scan soon after getting set up because it had detected a trojan (meanwhile I'm wondering how it had a trojan, shouldn't my computer be clean?). Halfway through the scan it's going through my Program Files, things that should NOT be installed at all, because according to the install/uninstall programs they're nonexistant on the computer. And some of these are things I'd uninstalled a few days before the reformat (The Sims, for instance) were sitting there getting scanned.

I open up my Program Files folder, and sure enough-there sit all of my programs that should definitely not be there. Is it possible that XP saved them for some reason? It certainly shouldn't have because these aren't vital programs to the system at all (The Sims surely isn't).

I'm very confused, and any help on the subject is appreciated.