Which updates are these you wish to install, I completed the game some time ago and the only updates there were then were the updates automatically downloaded when you first setup your steam account, and what a pain that was.
I'm assuming you've already got a retail version of HL2 installed on your PC and hence have already set up a STEAM account (which you must have done to get it working). We'll ignore for now the fact that VALVEs anti piracy measures are shall we say "interesting".
Again I'm assuming you are talking about "game patches". Simply:
- Run STEAM - Logon onto the Internet
The system does it automatically for installed software (in this case HL2). Unless you've set it not to auto update a particular game.
Though I would (especially if you are on a narrow band connection) try to find out first the size of any patches before downloading. Otherwise you could be logged on for a while!
Great game. Just finished it the other day.
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