Stop error!

STOP: C000021a {Fatal System Error}
The session manager initialization system process terminated unexpectedly with a status of 0xc000026c (0x0000 0x0000)
The system has been shut down.

Been having this for about a week....whenever my computer has been rested for a few hours...sometimes i get other error codes like

PNF_list corrupted

tried reformating like 3 times....still the same...does anyone know the cause...i was thinking it might be a memory problem

 

I'd say that is very likely.

http://majorgeeks.com/Memtest86_d4226.html

 

I tried Memtest86 for abt 2 1/2 hours....ran abt 3 complete tests....but no error was found...really feeling quite frustrated