I got twinview working in Win2K and Slack8 in 1/2 hr. Here's how:
Go to nvidia's linux driver page and read the README.txt
Really, it works. Answers all your questions and tells you exactly what to do. If that doesn't work for you. Post back here stating exactly what you did, and exactly what happened. "It didn't work", will prolly not get you the help you need.
Too tired....no sig.