|Install more RAM. If you know nothing about this, ask a friend about it. Installing RAM is easy, but you have to buy the right type.|
If you have an old PC, you may have difficulty getting the right type, but if less than 5 or 6 years old should be no problem.
If you visit http://www.crucial.com it can scan your system and tell you what type of RAM it needs. Or just use the selector for the make and model.