Cannot run game!

Since few days, I can’t run GMod.
I see that hl2.exe process is working, but then it disappears.
Please, help quickly, I haven’t much time!

Quick before it blows up <,< >,>

right click gmod->properties->advanced launch options-> put this -window -dxlevel 70 +mat_forcehardwaresync 0 and should run

EDIT:

If it doesnt run post specs and others should help

Nothing with the PC.

[editline]11:28AM[/editline]

But it worked.
Other Source games, such as NeoTokyo, Half-Life 2 and Team Fortress 2 are working fine.

Reinstall it.

Never mind, Storm’s solution worked.
Thread can be closed.