D-Link's probably the only router I haven't set up. But from what I see there, you want to enable the Virtual Server.
Name is just any name you want to associate with this setting, so that you will later remember why you set it. (Useful if you set a bunch of them.)
Private IP is the IP address of the machine you want the server to actually run on. If your D-Link router is acting as a DHCP server and "leasing" IP addresses to the server machine (and any other computers you may have), that will probably be something like 192.168.0.2 or 192.168.1.3. You can find out what your current one is by opening a command prompt (or DOS prompt in Windows 98/Me) and typing "ipconfig" at the prompt. From the pictures you posted in the other forum, the same server says that you IP address at the time was 192.168.0.100.
Protocol type is the type of connection you want to forward - either UDP or TCP. TCP in this case. Every game is different. Some need multiple ports with both protocols.
Private port is the port you want the packets to appear on on your machine. No reason not to make it 27015 just to keep it simple. Public port, likewise, is the port the whole wide (Internet) world will talk to to get to your name server. That definitely should be 27015. There is proably a way to specifiy a range of port addresses too, like 27015:27115 for example. The Help button there ought to say how. If you try different game servers, you'll find some that use a range. Finally, hit apply to put this rule into effect. What you've just told the router is that any time Internet traffic from the outside is sent to port 27015, just send that on unmodfied to the internal machine at 192.168.0.100 (for example).
Here's the first rub. If you're using DHCP to get your addresses and you have more than one computer in your house, your game server's IP address will change from time to time. That means that every time it changes, you'll have to go back into the router and change the private IP. It doesn't usually change more than every 2-3 days, and sometimes the same IP address is given to the same machine every time (especially if there's only one machine on the "inside"). If it never seems to change, you can skip the rest of this.
If you plan on leaving this server up a lot, you will want to allocate an IP address permanently. The DHCP server is probably set up to lease IPs in a certain range. You can find this out by looking at the page that sets up the DHCP server on the DLink. It will probably talk about an IP address range. It will reserve one of the addresses for itself (usually 192.168.0.1) and serve from .2 through .49 or something like that. Addresses ending with number larger than .49 are available for permanent allocation.
First thing is to do type "ipconfig /all" in a command prompt window and write down the DNS addresses listed there. You'll need them.
If you go into your game server's Local Area Connection properties (right-click on "My Network Places" or "Network Neighborhood" on your desktop and choose Properties from the pop-up menu and then double-click on Local Area Connection [or whatever your ethernet connection is called there] and click the Properties button), you would change the Internet Protocol (TCP/IP) (listed at the bottom of the list that "Client for Microsoft Networks" is in) properties to Use the Following IP address and then enter an IP address just after the range that the DLink serves. That is, if it serves .2 through .49, set your IP address to 192.168.0.50 or .51. Just match the first three parts exactly ("192.168.0" or "192.168.1" or whatever your DLink is serving via the DHCP server) Your subnet mask will be 255.255.255.0 and your gateway is whatever IP address the DLink reserved for itself, which is usually the .1 address such as "192.168.0.1". For the DNS server addresses, type in the ones you wrote down earlier.
Simple, eh?
port forwarding (gaming) 
Linear Mode
