Aargh! My weak spot... (and I thought I was immune to this thread...)
For some reason I just cannot resist when some rebel upstart offers an alternative to the MS experience, just for fun, or when I get a fancy to go back to the "good old days".
Some of the OS's sitting in my bin right now (not counting the Windows NT through XP cd's and the stack of Linux distros and live cd's I tried before finally settling on Xubuntu):
MS-DOS 6.22 (3 floppies)
Windows 3.11 (6 floppies)
OS/2 Warp 4 (3 floppies + 1 CD)
OS/2 Warp 4.52 (2 CD's)
FreeDOS 1.1 (the latest!)
BeOS 5 PE (1 CD)
Syllable OS (2 CD's:1 unmarked, 1 latest ver. 0.6.4)
NetBSD (2 CD's I downloaded in 2002, never got around to installing...)
QNX Demo Disk (Network and Modem versions, 1 floppy each)
MenuetOS (0.76, 0.83 and 0.85, 1 floppy each)
VisopSys 0.69 (1 floppy)
V2OS 0.64 (strangest of the bunch... 1 floppy)
And I fear it's not going to stop there...