One of the first thing that you want to do is to close all the useless programs. That way your CPU usage decreases and you will use less RAM ( random access memory). All the games use RAM, if there is not enough RAM your games will start to lag.
To check how much RAM you are currently using right click on the taskbar and hit start task manager. From there you want to click on the Performance TAB then you will have 2 graphs. One of them is CPU usage and the other one is Memory .
My current usage is 5% so that means doesn't do too much operations. Once you start a game or a program like Sony vegas, it can go up to 90%.
My computer has 8GB of RAM. Right now 1.71 GB is not available, if I start opening programs it will go high and it can go to a pint that the computer doesn't have anymore space for the game. If you have 4 GB and the game needs 2 GB the game will not have enough space. But a game doesn't use all the space the is required for it to run it uses about 60% and the rest is for backup.
