You can definitely do it with the nV RAID that comes with certain models of the nForce 3 and 4 chipsets. If all else fails you can also use software RAID to pull it off (setting up the drives as Dynamic Disks in Windows XP's Disk Management panel).
The big question is if it is all worth it in the end. I'd only do t if you were mirroring the drives for backup purposes. I would shy away from RAID-0 with two mismatched drives, though.