ATI Tray Tools + nvidia

You can't. Get yourself Rivatuner.

I have tried it on Nvidia cards but depending on the manufacture of the card it will not work.

I asked Ray Adams if he would do an NVidia of ATI Tray tools and he said he had no plans for an nvidia version, which is unfortunate because its brilliant for my old x850 pro and id like it for my 7800GTX

However i use ATITool all the time for my 7800, its invaluable for checking temps on full load after 15-20 minutes and you can overclock your nvidia card with it, it just has less functionality for nvidia cards( i.e. it doesnt give information on whether pipes can be unlocked, less fan control with nvidia and a few other things ), one thing it does have specifically for nvidia is seperate core and mem overclocking for 2D and 3D