Originally Posted by Shantei
Although do you reckon I should give what you did a go? It may be worth a try.
Mate, anything is worth a try if it can save $$$/hassles, if the topside of the card is heavily encrusted with dust then yes I'd suggest cleaning it as it can hinder heat dissapation.
You could try resetting the cmos as lhuser has suggested though there are several theories as to how to do this, refer to your manual if you are unsure, personally I don't disconnect the power cord from the wall socket I just turn the switch off (the reason being is that it gives a ground through the earth wire), you've stated previously that you've done most things with regard to troubleshooting so I would assume you've checked that the cards fan is still spinning up etc.
Last resort is to return to the basics, i.e. cpu, 1x stick of ram, HDD, video card and see if it will boot then.
When you do boot and get no display is windows loading or do you get instant "power off" when you hold in the start button to shut down?
Is this pc on a network, can you see it on the network when it boots? or do you also have "Halt on all errors" enabled in the bios?
The fact that you're not getting an error code at boot is somewhat perplexing, usually if a card is dead that is the first indication hence why I keep pounding on about troubleshooting. Do you get the single POST (power on self test) beep when you first start up?