I want to first update the MAC user that our VPN server is not a windows machine, but rather a Linux clientless PPTP VPN server. It certainly makes it very easy for any Windows user to connect using the screen shots provided on other pages.
We are keenly aware that many MAC users just seem to avoid anything Windows. So this information should let you know that while this might be very easy to do with Windows, it has nothing to do with Microsoft. If you cannot connect to a Linux PPTP VPN server with your MAC it is not something related to windows.
For Connecting a MAC to a PPTP server I simply refer you to this link
as it seems to be the best link on the web for doing this.
When your machine is set up to do PPTP VPNs, you have a new configuration pane. Go to System Preferences, and then Network. From the drop down list "Show" select PPTP. You may need to add DNS servers and domains to search if you can't find any of the machines on your VPN.