XP Pro Service Pack 3 NTFS Standard P4 setup w/Agp - nothing fancy here. Tuesday = Thunderstorm. Computer boots to MUP.sys then reboots. (I hate you POS!) What is the CHKDSK switch? (/r /s ???) It was probably was in the middle of some sort of WRITE operation when the power died. Any help appreciated. Wanna kill these ads? We can help!