Place to discuss Slackware
Have you read the README that I linked to in the previous message? I just browsed it and it mentions both "vesa" and the "nv" driver and apparently it should work as long as you have a working XF86Config with one of the above drivers (and others). There are some other changes it tells you to make to the config after installing the drivers. If following that README (the most definitive source of information) doesn't help then I highly recommend you bring the problem up on that forum I linked to as there are a lot more eyes familiar with your hardware and OS there that may have the secret answer (if reading the manual isn't enough).