From a client. Keeps rebooting. (also reboots in safemode at agp440.sys). Disable autorestart on system failure, blue screen of death appear:
STOP: c0000021a {Fatal System Error}
The Windows Logon Process system process terminated unexpectedly with a status of 0x0000034 (0x00000000 0x00000000).
The system has shut down.
Solution: As I was planing to replace all the winlogon.exe, csrss.exe, win32k.sys after other attempted solutions (ie. recovery console->batch $NtUninstallKBxxxxxx$\spunist\spuninst.txt, chkdsk, safemode, etc.), I noticed winlogon was already missing. Put mine (XP Professional) in (XP Home), problem solved.