fixed aspect ratio with 7950gt and vista

I've got a widescreen monitor and I still play a few old games that don't support widescreen. My gpu is an XFX Geforce 7950GT and while I was running Windows XP MCE my nvidia drivers were able to keep these games with their regular aspect ratio (black bars on the sides so no stretching). I recently upgraded to Windows Vista via a clean install, I'm using the latest drivers and all the options in the Nvidia control panel as far as I can tell are the same as they were under XP, including the option to keep a fixed aspect ratio. However, when I play my old games they stretch to fill the screen. Does anyone know if this is an issue with the Nvidia drivers for Vista, or is there something else I'm overlooking? Any help would be appreciated.