Ok to start with i have 2 operating systems installed, both windows xp professional, but 1 with sp2 and one with no sp installed. When I play Half Life 2 or CS:source on the 1 without service pack installed, after about 30mins of playing the game freezes for a sec then just crashes to the desktop. Occasionally though the game will wont do this and instead i will recieve a blue screen error. Its not very often i get the blue screen tho. Any way i installed sp2 on my other o/s (had problems with sp2 b4 so installed a seperate o/s) and installed hl2 and cs:s. Now it doesnt crash to the desktop, but instead i receive a blue screen error everytime, this happens on other games too, depending on what game it determins the time it takes for the error to occur, it seems that installing sp2 makes my system very unstable. i have recently reformatted so i dont believe it be a software error, i have recently replaced my mobo(other was faulty) and the rest of my system is under 12months old.
 
My Spec:
Athlon Xp 3000+ Barton Core
ddr pc2700 512mb
120gb maxtor hd (in 2 partitions)
geforce fx5600 xt 256mb card
As-Rock K7S8XE
 
I have checked that all the bios settings are correct and that the fsb jumpers are set correctly on my mobo.
 
The blue screen i receive says something like machine_check_exception i cant remeber exactly. one other thing i would like to mention i used the microsoft memory module tester and run the extended tests over night. my ram failed 2 of the tests, lrand and erand. Therefore i think i need new ram but i want peoples opinions first b4 i spend my money on it, ive already ordered a new gfx card, a xtx geforce 6600 gt 128mb.
 
I would be greatful for any help people have to offer. Thanks