"Don't Make Illegal Copies of this Disk"

So says the warning on the new Microsoft cdroms I bought. That would imply that there are legal copies of the disks you can make, right? What would those be?

Every license agreement I’ve ever read states that it is acceptable to make a backup copy of the disk the software is stored on.

be careful, it’s on ly in america that you can make copies of legally owned software, in europe, the laws are different.