How to setup GameServer (Say Half-life), so that people will join online?

Hi..
I want to setup my own game server in my home. So people who have access to internet can join into my game server with granted access permission. I have..
1.Assembled Server & 128 grapichs card with Windows2003 std edition.
2.Two Lan adpater 1GBs
3. ADSL Modem (10 MBs Down/2 MBs Up link data rate
4. One LAN router with Wireless capability.

Please guide me to setup my own home server for Online Gaming.

Thanks in Advance