Unable to add mirror (RAID 0)

[Matt]

When I try to add a mirror via the command line
util "diskpart" I get the error "The command you selected
is not available with this version of Windows."
If I try via the GUI the option is greyed out.
Typing ver at the command line yeilds "Microsoft Windows
XP [Version 5.1.2600]"
also in the properties of my computer I have System:
Micorsoft Windows XP Professional Version 2002 Service
Pack 1"
..