I can't remember the exact order, but this is approximate.
PC:
DOS 4
DOS 5
Windows 3.1
DOS 6.2
DOS 6.22
Windows 3.11
Windows 95, a, b, c
Windows NT 4
Windows 98, a, b
BeOS
Windows 2000 Pro
Windows ME
Red Hat 6.1
Windows Whistler
Mandrake Linux 8.1
Windows XP Home
Windows XP Pro (running)
Mac:
Mac OS 6
Mac OS 7.X
Mac OS 8.X
Palm:
Palm OS 1.0
Palm OS 3.X
Palm OS 4.X
I'm sure i missed something, but that's long enough.