I have a couple of old macs and I plan to get some of the software to go with these, because chances are I will eventually have to restore the software, or something along those lines. I am buying this used, from eBay, so the disks will have been used to install software before. Because they have already been used and they will probably be in a single pack set (not family pack), will I be able to use them on my computers? Thank you!