The courts have evolved a set of criteria which, although not definitive, provide a gauge or scale for balancing the equities. The multiple copies for classroom use is a recognition that, under the proper circumstances of fairness, the doctrine can be applied to reproductions of multiple copies for the members of a class. However, the endless variety of situations and circumstances that can arise in particular cases precludes the formulation of exact rules in the statute. Your question speaks of personal use while asking about fair use. As to application, your specific mentions present different problems.
Computer programs are quite specific.
The Software License often comes on a sealed disk package that clearly states that by opening the sealed package you agree to be bound by the terms of agreement. If one does not agree to those terms, promptly return the unopened disk package and the accompanying items for a full refund. Clearly, the program is treated as copyrighted material allowing the purchaser to make one copy for backup or archival purposes, to transfer the software to a single hard disk keeping the original solely for backup or archival purposes. What is clearly wrong is when A buys a program and generously allows B, C, and D to make their own copies for their personal use. That is simply theft.