Gmod won't start

My game is installed, and I also have TF2 and L4D2 Installed (both have been ran once)

I have also verified the integrity of game cache and de-fragged the game files on all three games.

When i hit play in my steam menu to start up GMOD, my cursor does the little blue circle like its starting something… then it stops the little blue circle and doesn’t do anything.
Gmod never starts no matter how long i wait… I’ve tried reinstalling it to no avail.

Any help?

What are your specs?

http://speccy.piriform.com/results/9ulKVrycjPWWgOfUEB4Dscb

There’s a link to speccy.

That seems okay. Is it getting to the main menu? Is it crashing before it gets to the main menu? Does it just keep saying preparing to start?

Try doing these things
1: Right click GMod in Steam, and hit Properties. Click Set Launch Options, and type “-fullscreen”. Hit okay and try starting up GMod.
2: If that doesn’t work, add “-dxlevel 90” to it.
3: If that doesn’t work, delete all of that, and type in “-window -noborder -w x -h y”, where x and y are your monitor’s width and height, respectively.

On a side note, I like it better when GMod runs in a window like that, because I can switch seamlessly between that and other things while it loads, or is connecting to a server.