The DX5150 uses the ATI Radeon Express 200 chipset which uses the Sil3112 raid chipset, and unfortunately from what I can read here, the driverpack MassStorage still has issues with it.  I have a few of those and actually ended up here looking for a way to integrate those drivers since the DX5150's I have don't come woth floppies so installing XP with drives already in RAID is a no-no.