Fatal system error Win XP

Hello again.. the last answer worked.. lets try another!

I’ve re-installed XP, installed MacAfee Firewall.. but Virus scan wont work. I un-installed it. Then I updated Win XP. Rebooted to finish the installation and this..

Fatal System Error
Stop: c000021a
The Session Manager Initialization System Process terminated unexpectedly with a status of 0xc000026c (0x00000000 0x00000000)
The system has been shut down.

I re-booted… same message.. help!