Downclocking the GPU

I have an HTPC with 2600xt GDDR4 which runs fairly warm and I think my system sometimes freezes because of it. I know that with Ati's catalyst I can OC my GPU but since I dont play games at all on that PC and I use it only as a media center I don't need the whole strength of the GPU so I thought about downclocking the GPU so it would heat less. Is there someway to do that???

Rivetuner compatible with 2600xt?

Can someone tell me the steps to downclocking my 8800gts using Rivatuner. I'd like it to idle down in 2D mode like my old 7800gt did. Why didnt Nvidia do it in the driver?

On the Main tab, go the arrow button on the forceware detected bar, then system settings.

There you should have a couple of sliders to change core and mem speed, and have different settings for 2D, low 3D and high 3D applications. For some reason my mem speed will stay at the same OC settings in 2D, which is irritating.

I think there may be a couple of other things you have to do in the power user settings first, google it.