I have an IBM NetVista 8307 (P4 2.4 Ghz, 256 Mb RAM) and with the default configuration Knoppix only ran at 640x480. The solution was to change the BIOS setting in the Video section to give the video card 8 Mb of RAM instead of 1 Mb (default). Now it runs at 1024x768.

Hopefully this will help someone else out there. Knoppix is very nice--especially for burning copies and handing them out to coworkers, friends, and family. I've been using Linux for years and Knoppix now has made my "so do you want to try Linux?" suggestion so much easier.

Edit: the IBM is a temporary test machine at work.