It sure is possible.
Don't have a link handy, but search for an app called Power Strip.
I'm not sure, but the stock drivers may even have OC sliders built in. If not, just search around a bit and you'll find the info.
PS. Put a fan on the heatsink first, and if you plan to drive it very hard clean the heatsink off and re-seat it with some good heat grease.
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Lephturn - Chief Trainer
A member of The Flying Pigs
http://www.flyingpigs.com 
"My P-47 is a pretty good ship, she took a round coming 'cross the Channel last trip.
Just thinking 'bout my baby and lettin' her rip, always got me through so far."
- Steve Earl
