ok, this is going to be a long and complete as possible post. I had a 200GB drive with 2 partitions. Win XP Pro on C: and Data on D: I had OS selector on this drive. My second drive 80GB had Linspire Five-O on it. I decided to scrap Linux, so I removed that drive, made the XP disk a slave and installed a new 250GB drive as Pri, Master. Went to the BIOS to remove the 2nd drive, so only the new 250 is showing. Installed Win XP Pro on the new drive. Everything is fine. Re-enabled the second drive in BIOS, rebooted all normal, got access to my files on the other drive. Now I want to be able to boot back into the other OS. I go and install OS Selector, it finds both XP systems. I can boot into either from the choice screen form within windows. I configure the old XP to change the order of the HD's so C and D would be as they normally should and everything works. However if I set the OLD XP to default, and reboot everything is fine for 1 time. When I reboot again, I get a flash of MBR ERROR 3 and it boots the NEW windows. I can not seem to get this to boot to the old XP by default. I did remove the new disk and boot of the old one, and removed OS Selector from that drives MBR thinking there might have been a conflict. But I get the same issue still. Please advise.... Thanks!