Hi my name is ***** ***** I will be the expert working with you today to help and resolve the problem you have posted.
As you stated you have purchased the Printmusic software several months back however you have a 30 trails or 30 days to register from the time you have insatlled it. If its not a trial pack and has been purchased then you can insall it anytime you want no problem with registring the product.
Now on the desktop part if the Printmusic has a multiple computer install then only you can install it on the other computer and if its a single user license then you will not be able to get it installed on the desktop computer.
For midi cable check the links given below.
Let me know if you have any question.