The community is also a great place to check out. Try these places for help from other users:
Please review the Third-Party Game Support topic to determine whether your question should be directed to the game developer or to Steam Support. Sending a support request to the wrong party may result in a delay in processing your request.
Retail CD Keys for Deus Ex: Human Revolution that match the following format can be activated to a Steam account:
12345 - ABCDE - 678FG
Unlink most Steam DLC or addon content, The Missing Link will appear as its own entry in your Steam library. Double-click this game to install it.
If you're encountering issues when launching or playing Deus Ex: Human Revolution, make sure everything installed correctly.
Exit Steam entirely.
Browse to your Deus Ex: Human Revolution installation folder (Usually C:\Program Files\Steam\steamapps\common\deus ex - human revolution\)
Run the following installers:
Reboot your computer and test the issue again. If the issue persists, contact Deus Ex: Human Revolution support.
To install the Augmented Edition content, load the Steam client and navigate to your Library. Click on the blue text next to the Search box and select "Tools."
Double click on "Deus Ex Human Revolution Augmented Edition Bonus Content."
Once the installation is complete, you can find the Augmented Edition content in the following directory:
If the above does not resolve the issue and you are running Windows 7 or Windows Vista, please complete the instructions in our Windows 7 and Vista Troubleshooting FAQ.
If you are running in Windows XP, take the following steps: