If I tried to touch the back of my HD4870, I`d lose my fingerprints! If you could hold a finger on the back of yours for several seconds it was running quite cool for a GPU (I think Human skin blisters at 70 degrees).
Not having a GTX260, I do n`t know how it behaves with no drivers loaded, but it sounds as if the fan was running at a high speed when you were reformatting and reinstalling because of a built-in failsafe in the cards BIOS.
Oh true I heard the 4850 4870 run really hot. For ur card, did it in any way damage anything?