Cross platform Hard Disk encryption?
TrueCrypt is cross platform.
TrueCrypt currently supports the following operating systems:
Windows 7
Windows 7 64-bit
Windows Vista
Windows Vista 64-bit
Windows XP
Windows XP 64-bit
Windows Server 2008
Windows Server 2008 64-bit
Windows Server 2003
Windows Server 2003 64-bit
Windows 2000 SP4Mac OS X 10.6 Snow Leopard (32-bit)
Mac OS X 10.5 Leopard
Mac OS X 10.4 TigerLinux (32-bit and 64-bit versions, kernel 2.4, 2.6 or compatible)