Slackware9.1? And you did the 2gb install? (its a bit n00bish, but it installs most packages that u will need)....ive installed it 3 times myself (all in the same day) but that was cos I was finding it hard to setup a dual boot system with XP on too....
Once id finally got it working fine, when i booted Slackware9.1 i was left at a root prompt, in which when i type 'startx' my monitor would flash ant fail to load X and go back to the root prompt.....after typing 'xf86config' it asked me a load of questions about my peripherals, gfx card, and monitor refresh rates, after i did all that it still wouldnt work....I went to nvidia.com and downloaded the linux drivers, copied them to somewhere i would find them on a ext2 partition and then used the cd command to navigate to them and ran the install command, after doing this i ran 'xf86config' again and then 'startx' worked
If uve left out X on your installation, then maybe thats why there is no such command (dont know if its possible to leave it out though, but prolly)....
If you havent, try reinstalling Slack, but choose the default 2gb installation option
Good luck :P