After reading `man depmod`, it appears you've screwed up your /lib/module/$(uname -r)/ directory (I'm assuming you're using the standard 220.127.116.11-smp kernel, in which case it would be /lib/modules/18.104.22.168-smp). Your modules.dep files (and possibly some map files in the same directory) are probably only pointing to acpi, which prevents other modules from loading, therefore making your system a brick. I think you could fix it by reinstalling the kernel-modules-smp-22.214.171.124_smp-i686-2.tgz package (available here: http://slackware.osuosl.org/slackwar...smp-i686-2.tgz
or from your install CD/DVD [on disc 1, in the slackware/a/ directory] or another Slackware mirror). Try `upgradepkg --reinstall kernel-modules-smp-126.96.36.199_smp-i686-2.tgz`.
You'll probably have to reinstall your ATI drivers after reinstalling that package, but I'm not sure. Also, if you're using a non-smp kernel, you should use the kernel-modules-188.8.131.52-i486-2.tgz package instead, available from the same places. If you compiled your own kernel, I would recommend switching back temporarily to the huge kernel and rebuilding your custom kernel. It *may* be possible to compile your kernel again and perform a `make modules_install` in the source directory without switching to the huge kernel first, but I'm not sure.