Are you running VNC on windows XP? If you don't have an admin password assigned, I think VNC requires that you set up a password to log into the PC.

Also, you will need the IP of the PC. If it is behind a router, I think you need to know the subnet as well. I'll fool around with it tonight and figure it out.

I'd just grab the IP from www.whatismyip.com

You might need to open some ports if you are using a router -- that was my past experience on another device, anyway.