I know there are tools that can actually write their settings into the video card BIOS. Thought that Ntune or indeed RivaTuner could do such a thing.
Sorry, my bad.
Personally speaking, my head is totally not into overclocking. If I require the speed for anything in my PC I will get the components that can deliver by default. In general I carry the opinion that when you start overclocking, you deserve every trouble you get.