Hi,

I have recently installed windows xp on a hp compaq P4 2800 MHz ..2800/533 with 256 DDR/333

I recently started my computer and now I GET a bsod. It says Stop C000021A {Fatal System Error}
The session manager initialization system process terminated unexpectedly with a status of 0xc000026c(0x00000000, 0x0000000) The system has been shut down.


thanks
Check your memory with memtest. It is free and thorough.

www.memtest86.com

Let's start there.
You may need to re-seat the RAM module and you should certainly add some more RAM

Click the link below for more info.why does the mem test take a long time.  I went for lunch came back and its still RUNNING.  I'm about to go home now from work and it is still running. Its been over 2-3 hours.  How long should it take??I run them overnight sometimes. If there are no errors showing then your RAM is OK.GoBack Causes a Stop Error C000021aI got some errors showing in the errors column as it is running now.    Errors = 95633     Ecc Errs= 0

Does this mean I have BAD memory??

YES it does. Have you tried a different RAM module?

Are all your fans running properly?If you have more than one stick of ram you can play musical ram chairs with them.