computer lock up while playing games

[Weetbix]

hey ev1 i hope someone can help
well i have been having a major problem for about 6 months it poped up overnight and i can seem to find out the source
the problem is while playing online games call of duty, battlefeild vietnam,medal of honour, my system locks up the screen becomes scrambled then about 5 sec later the whole system locks i run teamspeak and i can still talk and hear for about 5 seconds after the screen scrambles.
this problem is on and off sometimes i can play for hours or days even with no probs sometime 2 min after entering the game it locks and scrambles the screen. i went from a winfast A340 128meg video card to a geforce fx5700 256meg to try fix it but same prob
my system is
amd sempron 2800+
GA-7s748 motherboard
1 gig of 333 ram (2 x 512 sticks)
geforce fx 5700 256 meg video card
ata raid card
network card
3 120gig hdd's
2 roms
i have tryed a few things to fix the prob but to no sucess i have
-rolled back from win xp to win 2000
-tryed the drivers that came with cd for my graphics card i am running 66.93 nvida driver now i tryed 56.56 same prob
-i have the latest direct x it is needed to play the games that im having trouble with
- virus scans i run nortons but i also use bitdefender and panda online scans i am clean
-tred removing non nesserary hardware (network card, 2 hdd's , raid card , cd-roms ) still same
- tested my ram ( i have 2 sticks i tryed one at a time in
the 3 ram slots on my mb unless both chips are gone my ram is fine )
-run sandra burnin wizzard and test modules everything ok


the problem only happens when playin games all other programs seem to be fine. the problem started with call of duty but now COD:UO, medal of honour and battlefeild vietnam are also doing the same thing.

i have spybot and adaware and i run a winstock fix after i find malware.

im guessing and thats what it is a guess that the problem is my motherboard because i had the prob with my old graphics card as well and i rolled back to win 2000 same prob i dont have another motherboard to test this so my last option is to take it to the shop so if anyone has any sirgestions i would be greatfull if you need to know something else or i forgot something let me know ill try to tell ya.

[Weetbix]

i just ran 3DMark05 and i got the same problem screen scrambles and computer locks up ?

[nimbu]

Dude from what you have said sounds like the mobo to me

[iranu]

Have you cleaned the inside of the pc? Dust can cause quite an increase in temps. Get one of those air blower cannister thingys or as I prefer a large soft paint brush and remove as much dust as you can from all heatsinks etc.

Remember to unplug power and ground yourself by touching the case before poking around inside. Let us know how you get on.

[Ravens Nest]

Check to see if your heatsink & fan is mounted properly onto your CPU as i had a similiar problem with crashing which was due to overheating..

There was a small gap between the cpu and the heatsink, also i had too much thermal compound on there too, you only need a tiny amount
(only enough to cover the area and only slightly thicker than transparent)

And as Iranu said, check to see if theres a lot of dust built up on your fans and heatsink if so, take them all apart and clean them.

Also what PSU have you got as you have a lot of stuff running on that PC, so that may cause instability due to low voltages.

Also a BIOS upgrade sometimes helps
(But only do this as a last resort, as they can sometimes go wrong effectively making you motherboard useless in the process)
http://www.giga-byte.com/Motherboard...S_GA-7S748.htm

[Weetbix]

hi ev1 thanks for the help it ended bup being the mother board so i bought a abit nf7-s