If your PC "lags" while you are in West Arch it could be because it can't keep up with the screen refresh requirements of your video card. There is a way to minimize this by turning off all the background programs that are not needed when game playing.
I used to make and repair computers but I have a hard time remembering which programs these are. Instead of turning them off one at a time I use a piece of software called "Game Booster". Using this program, and also cleaning out any spy-ware and the registry, relieves the load on the processor so it may spend more time servicing your game.
The software is free and can be found at:
http://www.iobit.com/It does a good job for me.