Your not going to blow your card just because your gfx card is able to get a high fps. And the 8800 GT isn't an old card.
Yes it's not new. But it's still a powerfull card. It's infact the only card in the 8 series that isn't really an 8 series card. It's tech is series 9. The 9800 GT and the 8800 GT is basically the same card. (more or less...)
If you still want to lower your fps then just search for D3D Overrider and force vsync and Tripple buffering.
That will keep your fps bellow your screen refreshrate.
That would be 60 for all lcd screeens. It is possible to set higher on some lcd's. My monitor can do both 60 and 75. It doesn't really go above 60, as LCD's don't "Refresh" the screen. Refreshrates on LCD's are there only for backwards compatibility.
But it does affect vsync. So if you really feel like having 75fps instead of 60fps. then setting your refreshrate to 75 (or higher) will increase the vsync cap.
But really. Do you really need more than 60fps? it's not like your eyes is able to see faster then... what is is?.. hmm. 25 or 30fps... something close to that.
