Just getting started have questions on setup

[want2know]

Hello, thank you in advance for reading my post.
I have downloaded the software but have not installed it. My current office setup is. Computer with windows server 2003 (two NIC’s) and 18 clients using windows 7 Pro. The layout is a router provided by the ISP for internet access; router is connected to a 12 port Dlink switch, from the switch it connects to the server NIC1 (192.168.100.187). NIC2 (172.18.45.1) connects to Cisco 24 port switch. All clients connect to network through the Cisco switch. The server has installed Windows Server 2003 32bit Enterprise, Active Directory, DNS, DHCP, File and Printer. Also have another computer used for file sharing. We also plan to have a share point. I volunteered to set this up and it works fine all clients have access to internet and file access. This is for office 1 of 2. Once the VPN is working in office 1 it will be replicated in office 2. Office 2 is 20 miles from office 1. My question, I have read through most of the tutorials, is the soft ware to be installed on the current active server or a separate computer? Also if software is installed on separate computer (with two NIC’s) is the computer placed between the Dlink switch and router, where all traffic flows. What is the best way to set this up? I have a network that is working and I want to do this right the first time. I am not asking to be spoon fed, just want to stay on the right track. Thanks in advance for your input and suggestions.

[BoredAus]

Would be nice if you could draw a network schematic diagram to better illustrate your setup.

[want2know]

image of current layout as requested.

[thisjun]

I think installing VPN server in Windows 2003 is easy way.