I tried redownloading and reinstalling the driver (from
http://support.amd.com/us/gpudownload/windows/Legacy/Pages/radeonaiw_vista32.aspx?type=2.4.1&product=2.4.1.3.13&lang=English). It seems to be working now. The PlayVideo() function doesn't seem to be working (in the example project) but it doesn't come up with an error, and the 3D example works. I downloaded the Full Software Suite from the page, It said that the drivers were already installed (from when I installed them before), but I overwrote them and I works now. Here is the info from the Catalyst Control Centre:
Driver file: atikmdag.sys (8.1.1.882)
Card type: ATI Radeon X300/X550/X1050
Driver Version: 8.593.100.0
Adapter RAM: 128.00 Mb
SOFTWARE DRIVERS:
Catalyst Version: 10.2
2D Driver version: 8.01.01.882
Direct 3D Version: 8.14.10.0647
OpenGL Version: 6.14.10.8545
Thanks for all your help.