To date, I've purchased all my OS (OEM versions), which would explain why I only recently acquired Windows Millennium. At this pace, I figure I'll finally get XP Home (SP3?) around 2005 (by then most of the security flaws and software bugs should be solved).
I'm the only person I've ever known who actually purchased a Winamp license, about two months before it went freeware (of course). I actually don't have much on my PC right now because I recently formatted, but I purchased:
Winzip
MusicMatch Jukebox
Paint Shop Pro
Veritas Backup Exec (free upgrade to Backup MyPC by Stomp Inc.)
I have a bunch of other stuff that isn't currently installed, whether it came bundled with other hardware/software or I purchased it outright.