I agree with andyford that the Registry and config files are your basic to choices. For the registry, take a look at Win32::TieRegistry. If you're not storing any path address in the registry, then you should be able to move your program around to other directories on that same machine, but not to another machine, without reinstalling. This can be seen as good or bad, depending on what you want.

One of the advantages of Eudora for email, at least the older versions that I still use, is that you can pick up the whole directory tree and copy it to a new machine, and everything works. That's really nice. They put the config and registration info in a local config file to make this possible. You can still incorporate a user name in an encryted key to give some small measure of protection. For this approach take a look at modules like Config::INI::Simple, Config::IniHash or AnyData to read and write config files. The config file often goes in the same directory that your code is installed in.