Half Life 2 Won't Start HELP!

[griffiths121]

Hi I Love All The Half Life Games And I Have Finally Got HL:2 And When I Run It It Get The The Part Where It Loads The Menu And Then My Pc Just Restarts Its Self Please Help I Really Want To Play This Game

Specs
AMD Athlon 3800+ (2.4 Ghz)
GeForce 6500 PCI-E
512 DDR 400 Memory
80 Gb Hdd

 

[bbson john]

Verify your game files

 

[Beerdude26]

Run the Steam Diagnostic Tool:

steam://support/?Issues=*

 

[griffiths121]

P.s Thanks everyone else for the help your all great!

 

[Pi Mu Rho]

So everyone is happy then. Good.