I was thinking about this last night and came to the conclusion that it would be very difficult for a major fire.
Most likly thing to happen would be the PSU/GFX/CPU goes pop then the computer turns off.
If it does turn into a fire then its sealed inside the metal case and there isnt exactly that much fuel inside there for the fire to consume so it would burn out quickly.
Most likly thing to happen would be the PSU/GFX/CPU goes pop then the computer turns off.
If it does turn into a fire then its sealed inside the metal case and there isnt exactly that much fuel inside there for the fire to consume so it would burn out quickly.
I was thinking about this again too. I had a computer where the flames exited the case. Sure it was a spectacular bang, but if there had been anything flammable above the computer at the time it would have gone up in flames too.
But basically, the card will still survive just fine even with a non-functioning fan. I'd say the only risk is if the heatsink itself becomes detached from the card, but if that happens without you realizing it, there's probably other issues with your computer that you need to work on anyway. 
