Call of Duty MW3 lags in campaign after installation of Quake and Doom series

Question

I've had CoD MW3 installed on my PC for a few months and I've had zero problems with it. Last week I installed the Quake and Doom series on my computer. Now when I play MW3 the game constantly lags and is impossible to play. I read somewhere that MW3 is based on the Quake 3 engine -- is it possible that the Quake series I installed over wrote MW3 files with original Quake files or Quake or Doom installed something that is conflicting with MW3?

OS: Windows 8 64bit
Mobo: GIGABYTE GA-Z68AP-D3(R2.0)
Graphics: EVGA GeForce GT 640 2GB 128-bit DDR3

Answer 1

Modern Warfare 3 does not use an ID game engine.

The only Call of Duty game to use an ID game engine was the first Call of Duty game, like many games at the time (Medal of Honor, Return to Castle Wolfenstein and many other games also used ID Tech 3).

Every game since the first has used a heavily modified game engine based upon ID Tech 3, called the 'Infinity Ward Engine' however the two most recent games (Modern Warfare 3 and Black Ops 2) use their own custom game engines (The Modern Warfare 3 engine, and The Black Ops 2 engine respectively). Even if these are based on ID Tech 3, there isn't going to be much of the original code left by this point.

However, even if the game was running on ID Tech 3, it is extremely unlikely that the installation of Quake 3 or any other ID Tech 3 game would cause an issue with any other ID Tech 3 game - all of the installations are in their own folders and the game engine and assets are self contained within these folders.