I thought about making a new thread similar to this one, but I'll just take the freedom to post here, despite this being 5 months old. Looks ok here, dupe threads suck.
MS OSes
DOS
win 3.11
win 95
win 98
win 98 SE
win ME
win 2000 (job at hosp.)
win XP (Home+Pro flavours)
Tried Vista, will
never allow it on or near my machine or networks. My trip with MS ends here. Long live
GNU !!
GNU/Linux OSes
Knoppix (going live was awesome)
Linspire
Freespire
Xandros OCE
Ubuntu
Kubuntu
Xubuntu
GNUsense
PClinuxOS
Sam Linux
OpenSUSE
Fedora
Mepis
Mandriva
Damn Small Linux
Puppy Linux
Zenwalk Linux
Linux XP (in VM)
...and various specialized live distros like Trinity Rescue Kit not worth listing as "OSes"...