I assume it's a "built by ATi" card since most of the 128MB 8500LE's around are (that's what you bought, right?).
As NBD said, download the latest drivers, Multimedia Center and DVD Player from ATi's website. You'll need your ATi installation CD in the drive and have the CD code handy to install the DVD Player. The ATi MMC is superb, I suggest you use it for DVD playback as it is optimised for use with ATi cards and the resulting quality is damn good.
The latest drivers have a much more simple interface while being more functional. They have moved to a slider-based system for quality/performance settings which will make things a lot easier. You don't have to worry about what the individual setings mean, that being the case, and the default setting should be just fine for starters. Enjoy.
Opteron email@example.comGHz (stock HS/fan), Asus A8N-SLI SE (passive NB), 1.5GB RAM (2:3:2:5, 2T), WD Raptor 740GD 74GB, Maxtor DM10 300GB, Asus EN7600GT SILENT@???, M-Audio Revo 7.1, Nebula DigiTV, Dell 2005FPW, Enermax 431W Active.