Question: I have a P4 running on windows xp pro sp2 and it keeps on resarting over and over. I tried chkdsk and scanning with my antivirus. I tried one setting so it would not restart, and I got that message: c000021a fatal system error the windows logon system process terminated unexpectedly with a status of 0xc000001d (0x00000000, 0x0000000). The system has been shut down. Now my comp only works in safe mode. What can I do?