livecd as of 22-Dec-2002 does not support KT400. when booting livcd system hangs when detecting ide chipsets hangs @ VP_IDE VIA Unknown Southbridge [TXT] livecd-basic-x86-200..> 22-Dec-2002 00:19 39.7M
So I've searched the LKML, bugzilla and asked Lolo about this issue. You can find valuable information here: http://bugzilla.kernel.org/show_bug.cgi?id=14 Lolo created a patch some while ago which took care of recognizing PCI stuff. If he finds this patch I'd be happy to apply it. AGP support is quite experimental I guess and so we shouldn't include that until 2.4.21 gets released.
kt400-agp support is now part of xfs-sources-2.4.20_pre3. It should work so I am closing this bug. If you encounter serious problems (which I don't expect) please feel free to contact me or file a new bugreport. :)