Kiith:
Do you have Steam installed for CS/ the other HL mods?
Steam is their new multiplayer network, and from now on to upgrade and play the mods you have to use it.
If you're using an old version of CS like 1.5 or lower, you can't play... until you D/L steam.
go to
www.steampowered.com and download the steam client.
Register in the program, be prepared as the 1st time you log on it will take forever (steam is horribly slow, unfortunately)
Then you want to go to Games on the main menu. Double click the mods you want in Available Games, and be prepared to wait at least an hour as it converts your existing games into the Steam Cache. (It is a huge disk space hog too - Steam with just HL and CS installed is around 1.2 GB on my computer)
Once that dialog goes away double click the new entry under My Games. It will bring up another dialog and start downloading the upgrades.... It will let you play after a while, you start the game thru steam and you're in at the main menu of the game.
Be Warned: if you have anything less than a 600 mhz it can get really bogged down... You don't want to run other stuff while steam is running games/downloading.
You can use it (I've played CS with my 333 P2) but it takes forever to join a game (seems like 5-10 min at times) However once in game the lag isn't too bad. (Using my p2 333mhz with a stb velocity 128, yes, crappy dated comp, my ping is around ~150)