monitor switching to standby

[nigel121]

athlon 64 3200+ (939)
asrock dual sata 2 motherboard
1 gig corsair value select ram
nvida 6600gt 128mb graphics (pcie)

i built this system bout 3 years ago mainly for gaming i play world of warcraft alot at the moment and while playing wow i find my monitor switches itself onto standby i dont have this problem when i play other games like football manager or rise of nations they run fine the other day i decided to install a game i played a while ago called guildwars but within a min of loading my monitor would switch off and while running the screen was full of artifacts so i underclocked the card using rivatuner i dont have this issue when playing wow anyway i turned the settings as low as i could in riva but im still getting artifacts im not sure whether its north/south bridge its the one with orange heatsink runs extremely hot and is the only source of heat u can feel when u place ur hand in the case my card has the stck cooler and i have water cooling on my processor im positive this isnt a heat issue unless its the north/south brigde 1 of which im presuming has some dealings with graphics i cant afford to buy both a motherboard and card and i cant afford a card without downgrading so basically i need to work out which im gonna have to replace b4 going ahead with it in the meantime im having to bodge it as i cant be having to reboot every 10 mins has anyone got any ideas of maybe how i can lower the speeds of whateva is under the orange heatsink or anyone whos seen similar probs let me know what their probs was thanks