i'm not sure what this "power save mode" thing is...
1) does your computer turn on? do all the fans go on? does hte fan on the video card go on? do you hear the beep(s)?
2) are you sure the power save mode doesn't have something to do with your monitor? try re-plugging it in. do you have integrated video? try plugging your monitor into the integrated video, go into bios, and disable it.. then replug it back into the 6600gt.
"Is virtue a thing remote? I wish to be virtuous, and lo! Virtue is at hand." -Confucius