If you want a new license key, I suggest you to go to its official webpage and send an email to the developer (ConsultCommerce Ltd.). Moreover, according to the information on the developer's page, the last version of LoanAmortizer Enterprise is 4.3, but there is no information that this version works with Windows 8.1. "Runs under Windows 95, 98, 2000, ME, XP, and NT4".