It's pretty much the same for AMD's web site. Upper right of the screen, you'll see the "Find a Driver" pull down. Just mouse-over it.
Component Category: Select Desktop Graphics
Product Line: Select Radeon HD Series
Product Model: Select Radeon HD 5xxx Series PCIe
Operating Systems: Select Windows XP - 32 Bit
and click View Results. This will bring you to the appropriate Driver Download Page. Click the download button for the Catalyst Software Suite, which includes the driver.