Updates are defined as enhancements to the original package that you purchased. Once the package has been updated, the old package should be destroyed or used solely as a backup. Again, it depends on what the software license says. Some licenses say that software can be used both at home and at the office. Some say that the program can be used on several machines, provided that no two are running at the same time.
Some programs are very restrictive and say that the program can be used on only one machine.
If you don't have access to the license or if you find it ambiguous or unclear, make sure you check with someone before you copy anything. Consult the University Bookstore's Buffalo Chip if you have questions about software licenses.