Windows XP does not support disks greater than 2TB. To use the disk with Windows, you will need to use a compatible operating system that supports disks greater than 2TB (e.g. Windows Vista, Windows 7). This limitation is in Windows XP, and is not something MacDrive is capable of overcoming.  

MacDrive has been tested and works properly with disks larger than 2TB under Windows Vista and Windows 7.

Apple RAID support in MacDrive 9 Pro is also limited to 2TB or less in Windows XP.