Your best bet is going to nVidia's website and talking to their support to see if they even offer support for Vista. There are companies that are not supporting Vista Beta testing in any way right now...and probally won't untill it's released next year.
Actually one of my good friends has RC2, and i'm soon to get it....it's one hell of a download from Microsoft though...and i'm not sure of the exact site to go to and download it from, but you may want to look around their website.
I couldn't find a site that had it for download, but my friend had the download burned to disk, and GW is working fine now that i'm on RC2. See if your dad has got the RC2, or wait a day and see if you can find it again though Microsoft.