Once you've managed to track down a crack or valid key for an old piece of software, so that you never have to worry about keeping track of it again, burn the software + the crack files to a disc.
Hardcopy backups are so useful. I have almost every version of MS Office saved this way - obtain the untampered ISO, once you verify a good crack/key for it, inject that into the ISO and then burn that to a disc. It removes all of the hassle.
Like tonight, after getting Office 2003 downloaded and installed, I saved the working product key I found online in a key.txt, and dumped that into the root folder along with the entire installer for Service Pack 3 - since the original image was only like 200MB, it definitely had the room for it.
So now anytime I want Office '03 on an XP system for the Aesthetic™, I won't have to futz with finding the right keys again. It's all right there on the same disc I'm installing from! And this would of course work just as well for video games, OS install discs, etc. given there's any free room to spare. This isn't as easy to do with floppy disk images, obviously, since they're usually packed to the limit.