Steam games not working

[mc_creeper]

One day I tried to run my Modern Warfare 3 and it gave me a blank screen so I rebooted pc and try Saints Row: the Third, it also gave me a blank screen. I got Crysis 2 to work and dead island but in dead island if I try send invites to friends the game stops responding. I have tried a lot of thing and even reinstalled steam. Nothing has worked. Now all games are not working.

System specs:

Core 2 Quad: Q6600 @ 2.4Ghz
Gigabyte G41M-Combo
4Gb 1333Mhz
Gigabyte GTX 550 Ti OC WF2
Corsair TX750 watt PSU

Steam is installed to my 1Tb external (Everything use to work fine)

 

[Brett928S2]

Hi

VERIFY your games in Steam... and run a hard drive test on that 1 tb external...

All the best Brett

 

[mc_creeper]

I have done both but it still doesn't work :/ If I verify my games most of them need a few downloads but then when I run them they crash and I have to re-download the same thing. I have worked out that its something to do with windows but my steam drive works fine on my friends alienware. I will mostly likely reformat windows and reinstall steam to an internal drive if I get a 1-2Tb drive.

Thank Brett anyway