Sometimes, simplicity is the best choice for both a technology solution and the corresponding tutorial that explains how to use the new solution. In this document, I will provide a clear, concise, systematic procedure for getting a Windows Server 2003-based PPTP VPN up and running. I'm using Windows Server 2003 with Service Pack 1 for this guide.
Add the Remote Access/VPN Server role to your Windows Server 2003 system
To add the Remote Access/VPN Server role, go to Start | All Programs | Administrative Tools | Configure Your Server Wizard. The first screen of this wizard is for informational purposes only and, thus, is not shown here. Click Next. The same goes for the second screen, which just tells you some things you need to have completed before adding new roles to your server.
On the third screen of the wizard, entitled Server Role, you're presented with a list of available roles for your server along with column that indicates whether or not a particular role has been assigned to this machine. Figure A shows you a screen from a server on which just the IIS Web server role has been added.
Figure A

To add a new role, select the role and click Next
To add the Remote Access/VPN Server role to your server, select that role and click the Next button to move on to the next screen in the wizard, which provides you with a quick overview of the options you selected.
Figure B 

The summary screen is pretty basic for this role
Take note: This selection just starts another wizard called the Routing and Remote Access Wizard, described further below.
The Routing and Remote Access Wizard component
Like most wizards, the first screen of the Routing and Remote Access wizard is purely informational and you can just click Next.
The second screen in this wizard is a lot meatier and asks you to decide what kind of remote access connection you want to provide. Since the goal here is to set up a PPTP-based VPN, select the "Virtual Private Network VPN and NAT" selection and click Next.
Figure C

Select the VPN option and click Next
The next screen of the wizard, entitled VPN Connection, asks you to determine which network adapter is used to connect the system to the Internet. For VPN servers, you should install and use a separate network adapter for VPN applications. Network adapters are really cheap and separation makes the connections easier to secure. In this example, I've selected the second local area network connection (see Figure D), a separate NIC from the one that connects this server to the network. Notice the checkbox labeled "Enable security on the selected interface by setting up Basic Firewall" underneath the list of network interfaces. It's a good idea to enable since option it helps to protect your server from outside attack. A hardware firewall is still a good idea, too.
Figure D

Select the network adapter that connects your server to the Internet
With the selection of the Internet-connected NIC out of the way, you need to tell the RRAS wizard which network external clients should connect to in order to access resources. Notice that the adapter selected for Internet access is not an option here.
Figure E

Select the network containing resources needed by external clients
Just like every other client out there, your external VPN clients will need IP addresses that are local to the VPN server so that the clients can access the appropriate resources. You have two options (really three! I'll explain in a minute) for handling the doling out of IP addresses.
First, you can leave the work up to your DHCP server and make the right configuration changes on your network equipment for DHCP packets to get from your DHCP server to your clients. Second, you can have your VPN server handle the distribution of IP addresses for any clients that connect to the server. To make this option work, you give your VPN server a range of available IP addresses that it can use. This is the method I prefer since I can tell at a glance exactly from where a client is connecting. If they're in the VPN "pool" of addresses, I know they're remote, for example. So, for this setting, as shown in Figure F below, I prefer to use the "From a specified range of addresses" option. Make your selection and click Next.
Figure F

Your choice on this one! I prefer to provide a range of addresses
If you select the "From a specified range of addresses" option on the previous screen, you now have to tell the RRAS wizard exactly which addresses should be reserved for distribution to VPN clients. To do this, click the New button on the Address Range Assignment screen. Type in the starting and ending IP addresses for the new range and click OK. The "Number of addresses" field will be filled in automatically based on your entry. You can also just enter the starting IP address and the number if IP addresses you want in the pool. If you do so, the wizard automatically calculates the ending IP address. Click OK in the New Address Range window; your entry appears in the Address Range Assignment window. Click Next to continue.
Figure G 
You can have multiple address ranges, as long as they are all accessible
The next screen asks you to identify the network that has shared access to the Internet. This is generally the same network that your VPN users will use to access shared resources.
Figure H

Pick the network adapter that gives you access to the Internet
Authenticating users to your network is vital to the security of your VPN infrastructure. The Windows VPN service provides two means for handling this chore. First, you can use RADIUS, which is particularly useful if you have other services already using RADIUS. Or, you can just let the RRAS service handle the authentication duties itself. Give users access to the VPN services by enabling dial-in permissions in the user's profile (explained below). For this example, I will not be using RADIUS, but will allow RRAS to directly authenticate incoming connection requests.
Figure I 
Decide what means of authentication you want to provide
That's it for the RRAS wizard! You're provided with a summary screen that details the selections you made.
Figure J

The RRAS wizard summary window
This also completes the installation of the Remote Access/VPN Server role.

User configuration

By default, users are not granted access to the services offered by the VPN; you need to grant these rights to each user that you want to allow remote access to your network. To do this, openActive Directory Users and Computers (for domains) or Computer Management (for stand alone networks), and open the properties page for a user to whom you'd like to grant access to the VPN. Select that user's Dial-In properties page. On this page, under Remote Access Permissions, select "Allow access". Note that there are a lot of different ways to "dial in to" a Windows Server 2003 system; a VPN is but one method. Other methods include wireless networks, 802.1x, and dial-up. This article assumes that you're not using the Windows features for these other types of networks. If you are, and you specify "Allow access", a user will be able to use multiple methods to gain access to your system. I can't go over all of the various permutations in a single article, however.
Figure K

Allow the user access to the VPN
Up and running
These are the steps needed on the server to get a VPN up and running. Of course, if you have devices such as firewalls between your VPN server and the Internet, further steps may be required; these are beyond the scope of this article, however.