Unless you own multiple copies of a software CD, or own a site license purchased with the CD, then it is ILLEGAL to install one software program to multiple computers. 

You have the right to make a 'back up' copy of any software program for safe keeping.

You can LOAN software, as long as it no longer physically exists on your computer. If the person you loaned it to does not erase it from their computer when they give you the CD back, then they have violated the law, and you have helped them do it.

If you are given a computer without an operating system installed, it is illegal to install a copy of Windows, for example, from your own computer's CD.  The only exception to this is IF your church has a "site license" from Microsoft Windows. Then you can install the same version of Windows to your Sunday School computer as you have in your church office because they are both part of the same site.

When you purchase software, you are only purchasing the RIGHT to USE the software, not the right to distribute it to extra computers.