DOOM game has problems running on Windows 7, which is why the game can be very slow and do not run.
For this purpose there FIX that improves the optimization of DOOM on windows 7.
Download the developers fix and install. Download here Win7 Fix Doom.
It is worth noting that the fix does not install if you have not installed the game Doom, perhaps during the installation will have to specify the folder with the game if you fix it automatically finds.