Can not start HL2

[Alpet]

I start the game and i get:

"The procedure entry point g_ScopeTraceStackDepth could not be located in the dynamic link library tier0.dll"...

I press OK and i get the same error again...
I press OK again and i get a:

"unable to load filesystem_stdio.dll"

I press OK and thats it :-(
nothing happens :-(

 

[irishbloke]

Erm i could be wrong but buying the game might help.