Like yourself, i have an ATI card, although yours is a bit newer.
One thing about ATI is that their drivers are updated almost tri-annually.
So you should visit the ATI site and check for updated drivers (and the new cards.... that probably will blow your 'older' card by then..)... (-:
anyway- try installing the drivers. if you have a scaled down version of a "full" card, ie "LE" model, then try the full model card's drivers!!!! Sometimes it works! Good luck. Windows drivers (on the windows installation cd are seriously outdated.