A:Due to the operating system limitation, Windows^® XP only supports MBR disk format, the MBR disk format cannot support the hard drive capacity over 2TB.
If you want to use over 2TB RAID volume to be your boot disk, below three conditions must be required:
1.Your operating system must be Windows^® Vista™ x64 SP1 or Windows^® 7 64bit.
2.EFI BIOS.
3.GPT disk format.

Please refer to following link to get more information.
Link:
http://support.microsoft.com/?scid=kb;en-us;946557&x=9&y=7
http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx