I couldn't really get the VNC stuff that came with red hat to work correctly either. If you go to
www.realvnc.com and download their tar.gz and install it, it works much better. Once you install the server from them, simply log in as the user you would like to vnc as and run vncserver at the command line. This will start a vncserver for that user. It will also tell you what desktop number that server is. Then when you start vnc from your xp machine enter the server name or IP address followed by ":1" without the qotes and assuming that your desktop number is 1. You can read about all this on the realvnc site. It works really well because you can have a number of vnc servers running at once.
I can SSH to my linux box at home and then log in as myself and start one server then I SU to another user and start a second server and then SU to root and start a third. Then I can vnc to patshouse:1 or patshouse:2 or patshouse:3. I use desktop 1 for my work, desktop 2 for screwing around with windows managers so I don't mess up my main desktop and desktop 3 for root access. Actually I don't really use the root access that much since I do most of that work through SSH.
Another neat feature of the latest server is that you can http to it on port 5801, 5802, 5803 etc. depending on desktop number, and view your desktop from a web page.
Sorry about the wordy post.