Thanks for posting your specs.
The problem is one or a combination of 3 things, Windows needs to be updated, the GeForce GTX 750 Ti needs the latest graphic drivers or Doom 3 needs to be updated.
Perform all 3 steps before trying to play Doom 3 again…
Update Windows 7 to the latest Windows updates, update everything.
– If you are not sure how to properly update Windows 7, I created a tutorial with a how-to video that will show you how to do it: http://www.cleartechinfo.com/how-to-update-windows-7-microsoft-windows-update
Update the GeForce GTX 750 Ti to the latest nVidia graphic driver update.
– The latest update was just released last week. Get it from here: http://www.nvidia.com/download/driverResults.aspx/95553/en-us
– After the latest drivers are installed, Restart your PC
Update the Doom 3 game.
– I am used to downloading and launching games via Steam or Origin launchers. Those auto-update your games, if not you can go into the settings to make sure they auto-update your games.
– If Doom 3 is not connected to a launcher like Steam, please post where you got it from, if you don’t know how to update Doom 3
Now that you finished all 3 tasks above, it is time to launch Doom 3. But this time launch Doom 3 a different way.
– You need to find the file that launches Doom 3. It is probably named something like, “Doom3.exe” or “Doom3BFG.exe”
– The file is probably in the “”C:\Program Files\Doom 3\’” or “C:\Program Files (x86)\ \Doom 3\” directory.
– If you have Steam, The Doom 3 folder could be in a directory that looks like this: “C:\Program Files (x86)\Steam\steamapps\common”
– “Right-click” the “Doom3.exe” or “Doom3BFG.exe” file. You will get a quick pop-up menu.
– Select “Run as Administrator”
Note: Yes, I know you are already logged on to an Administrator account. But right-clicking, then selecting “Run as Administrator” is an additive measure to solve problems. It has solved games not launching on my own PC even though I have performed all the steps above with no luck.