Well, I got something like that too, however, I got a ****ty 8400gs and a Gigabyte P35 and its working almost fine for wii games, and almost perfect for Gcn games... so, its good to have a nice videocard like your hd4850 I think ^^Here is my pc specs:
CPU: Intel Pentium Dual-Core E2140 OCd to 2.8Ghz
Mobo: MSI P35 Neo
RAM: 2GB OC 840MHz
PSU: Corsair vx450w
GPU: Sapphire hd4850 Toxic
will wii games run on this configuration?