If my computer is more than a few years old, or is running slowly, I need a new one.

Do you throw away your car just because your "check engine" light is on? Unless you are as rich as Bill Gates, you don't. You take it to your mechanic to have routine maintenance done. The same periodically needs to be done with your computer. After a while, they tend to develop a "waxy buildup" (hey, I work in a Dental School), and need some work done. Fortunately for you, I provide such a service.

Don't go telling the computer manufacturers I told you this. They would really like you to believe that you need a new computer every year or two.