TF2 is not loading

[The Evil Monkey]

I got a real problem, when I try to open TF2, the little windows saying that it's preparing to launch is there but when it finishes either it open for a second then closes or nothing visual happens but in my task manager "hl2.exe" is open.
I really need help

Thanks

 

[.[BORN]2kill]

What OS are you using? Did you try a reboot?