service pack problem

[misterfatal]

when i first got my computer, it ran all the service packs and windows updates fine. but when i installed my new video card and PSU, my CPU usage stayed really high. so i installed XP without any service packs, and it was fine , but i decided to try installing XP with service pack built in, and AGAIN my CPU usage is running high. whats the problem here?
btw, its a compaq sr1830nx. and i KNOW the hardware is fine because i ran it 7 months without the service pack and it was good,and that was with the GPU and PSU.

 

[LA1]

You know how you check the cpu usage ? instead of performance click processes and look at what is hogging the show.
or go through and end some,
you can also go to wininternals and download process explorer.

 

[misterfatal]

just system idle process is 90%+, i downloaded task info, and it says interrupts time placeholder is the one hogging the cpu usage.

 

[LA1]

you might try
click start
then run
type msconfig
enter
click on the start up tab <<<< not services>>>>
try disabling all and see what happens, or a few

 

[misterfatal]

nothing

 

[LA1]

so this copy of xp is it retail, oem ? burnt copy ?

the interrupts that are being generated could be from a failing peice of hardware.