Question: Can I make an extra copy of a music disc for listening in my car? What about a backup in case the disc gets ruined?

Answer: According to the opinion that halacha recognizes ownership of intangible intellectual property, the creator can limit the right to make multiple copies of his creation even for such personal use. In some cases, though, he might not object if the discs will not be played simultaneously.

According to the opinion that there is no ownership, it would usually be permissible when you would not consider buying another copy.

On the other hand, to make a backup copy would seem permissible even according to the opinion that there is ownership. You are not making unauthorized use of his intellectual property, but rather securing the copy that you purchased. In some countries dina d'malchusa allows copying for such purpose.

A similar halacha would apply to installing a program onto multiple computers. Many programs now specify whether the license is for single or multiple use. Some single licenses still allow copying on to a home computer and a laptop.

(See Emek Hamishpat, Zechuyos Yotzrim, Intro. 3:43-46; ch. 35:201)