The problem isn't the card or the ATI driver
, the problem is that for the most part there is no working AGP driver for the motherboard. There is a default universal AGP driver that installs with Windows, but it a generic one that only supports some of the AGP based chipsets (a cople from Via, old AMD based boards and a couple from SiS). The AGP driver is required so that the driver for the video card will work properly.
Yours is one of the SiS based ones (648FX) which hasn't seen an update of any kind since the last one for XP back in 2005. Give the thread thefabe linked to a good read and try some of the workarounds listed there, and hopefully you can get it working.