How many computers can you install a program you bought on?

You have to read the license that comes with each program. Generally, programs come with permission to install on one computer only. Some publishers allow for one desktop and one laptop so that when you take your laptop to work you still have access to the program you paid for. Others allow more installations, but if they do, then it is explicitly stated in the software license. For example, if you have a full-time student in the house, you are allow to purchase Microsoft Office Student Edition for a bargain price and install it on 3 computers. (If they have not changed their license recently.) It's best to assume that one disk=one computer until you discover differently through your research.