In no particular order:
1: Zone Alarm
2: Norton AntiVirus
3: WinACE (c'mon, does zip, rar, and ace)
4: Office 2k/XP (as long as I have Word, Excel and Outlook, I'm happy)
5: WinAMP (I turned it into my complete media center, real audio/video, AVI, MPEG, DiVX, TV, plus all the audio formats, et al)
I won't put my OS into that, because I'm assuming that it's a given. And since it IS Win2k, it'll automagically have IE6 on it. Plus my old DOS remnants. Maybe once I've taught myself enough VC++, I'll put it up on the list, but until then....