A while ago when I had a X800XT 256Mb card in my older desktop I did find a topic on how to get more out of an ATI card.
It may have been 'ATI Tray Tools' which I appear to have found at this site;
http://downloads.guru3d.com/download.php?det=733
I'd suggest putting in 'ATI Tray Tools' in google and having a read on the various user forums for information (and feedback) on this tool.
I don't remember where I first read about this tool but someone had posted about it with a lot of useful information - it was a year or so ago. I did use it for a period of time until I upgraded to a new desktop (the 8800GTX was a lot better than the ATI cards on offer - I'd been an ATI user since I stopped using 3dfx cards).