DEP problem!

[plutomaniac]

Exactly, as I said it has to do with your specific operating system. This is not the game's problem. First try a steam file integrity check as mentioned at the troubleshooting guide. Other than that, a guess would be that your graphics card drivers are not properly installed, old or corrupted and try to access the memory in an unsafe way causing the DEP stop error. Make sure Windows is fully updated via Windows Update and your drivers are updated (graphics & sound are more likely to cause issues). As a last resort, you can add the game to DEP's exception list.

Καλησπέρα!