HL2 won't start

[disk1of3]

I try to open the game but all it does is say "preparing to launch..." then it disapears. I've seen a few other topics just like mine but with no solution. But here are my specs if that helps more than the others.
Windows 2003
Video Card: Jaton px7800gt 256mb
1gb ram
3.0ghz pentium 4 processor w/2mb cache
please I've been waiting for a long time to play this game.

Edit: None of the games in the list in steam will start.

 

[Barney Fife]

try updating and validating game files, also make sure you are logged into your steam account. Make sure your video and sound drivers are up to date, and you did defrag the disk.

Good Luck.

 

[Bounty_Bam]

try opening it from the c/program files...etc... or re-install. also, try pressing ctrl, alt delete and close down any process that arent neaded (like msn, powerDVD)