Been happily running XP off a pair of WD Raptor disks configured as RAID 1 under the control of the on-board PROMISE 378 controller on my MSI 875P Neo-FISR (PCB 1.0). Last week the Promise controller Bios reported that the raid 1 array had gone" critical". I could still boot XP from the surviving drive. By trial and errr I identified which disk had failed and attempted to rebuild the array (option 5) which copies from the survivor to the failed drive. Rebuild appeared to be working, but at 8% complete the array again went "critical". I figured the target drive was stuffed. Next steps - ran ChkDsk across the survivor. No errors found. - replaced the target drive with a brand new WD Raptor - reran the rebuild process same error .... goes to 8% copying and the array goes "critical". Anybody got ideas as to what might be wrong and how recover? Various combinations of deleting/re-allocationg the array have been tried, but the rebuild fails at the 8% mark. System still runs on surviving drive, but I want my RAID 1 back! Cheers D.