Microsoft Windows
XP (32-bit), Vista (32- and 64-bit) & 2008 Server

IBM AIX
5.2 & above

Sun Solaris
10 and above on Sparc

Hewlett-Packard HP-UX
11i v2 & above (Itanium)

Apple Mac OS X
10.5 & above (Intel Chip)
Current version: 4.3, 5.1 ships soon!

Linux
Kernel 2.4, 32 bit
Kernel 2.6, 32 bit
Kernel 2.6  64 bit