VPN network not working

HI, this is my situation, i'm using Windows 2000 server. I set up a VPN network. Then, i tried loging on with my other computer in the network and error 721 came out saying that there was no response from the server when it was authenticating User name and password. Then i tried logging on with a dialup computer. Same error. Finally i used another computer with broadband and it worked.. However my other 2 computers cannot log into VPN, why is that? All the computers are on WIndows XP btw except for my server which is on WIndows 2000 server

Thanks yo

The other two computers appear to be dialling up and that error is because the are expecting an ISP to answer. Look slike VPN is setup incorrectly. Admittedly I know nothing about VPN, but I know a lot about connecting issues.

The last computer probably worked because it wasnt trying to DIAL.