Each key is locked to specific hardware. If you need to disable a key to free one up for another PC you'll need to ask Alibre or your reseller to do this. It won't be a priority for a retired licence, but should not be a problem to get this done.
Typically you just install the software, at first run it should ask you for username/password - an internet connection is needed (there is a way round this if your shop PC is not internet connected). It should sort out a key automatically. If you've been trying other things it might be good idea to delete the alibre.license file first (note the American spelling in the file name - it is a hidden file).
EDIT - hope shop PC has old OS, v11 won't run on Win7 and may be difficult to get to run under Vista.