The 800 aiw's capture part still doesn't work with the fglrx drivers, so don't use the fglrx driver, use the open source radeon driver instead, which under xorg 7.2 should give you 3d acceleration.
Now, for the AIW part, there is a hack available, but for this hack to work you'll need to have your x800AIW working under windows, so that you can steel 1 file from windows and configure-it on your Slackware installation.
The following link is for a Ubuntu, but you should be able to get it working under slackware. I you can't, say so and I'll try to give you more help:
http://www.ubuntuforums.org/showthread.php?t=273291