crashes the moment i start furmark.
I would try the card in another computer (friends computer? spare computer?) just make sure it has a suitable powersupply and you remove the old card's drivers first.
Make sure your using original/stable bios and not overclocking past manufacturers stock speeds for the test.
If it still fails the tests then I would suggest doing an RMA or if it is no longer under warranty try underclocking it until it is stable and/or remove the heatsink fan assembly and check for any signs of damage or poor thermal contact (dried or cracked thermal transfer material over cores, or more likely the VRM MOSFETS.) Also you can get a magnifying glass and carefully inspect all the tiny SMD capacitors and resistors that are all over both sides of the cards for damage (from mechanically breaking them off) or in the odd case of them exploding (which is a problem on some cards, eg. overclocked 67xx and 57xx cards in particular). If you find a damaged component it is not impossible to repair it yourself. If you do not have the skills/knowledge to do these kinds of things then I'd suggest pawning the card off as a 'faulty / parts' auction on eBay, you should get at least a few $$$ for it.
Edit: Also inspect the PCI-e (motherboard) connector pins for damage. If they appear dirty, clean them (google). Check the PCI-e power connectors and PSU cable plugs for signs of burning, if some of the pins/cables have charred then current will most likely not pass through it sufficiently and the card will be unstable, this kind of thing can happen - not surprisingly - on high-power cards like 5970, 6990, 7990 etc.