VirusScan Enterprise has three types of License. 1yr, 2yrs and Perpetual. That option is configured in the Setup. The product doesnt have any kind of License Key or File etc. There is also no Trial/Eval option as far as I know.
I cant remember off the top of my head how to find out what of the three options your PC(s) have installed, so it may be worth re-running Setup and selecting 1yr if you're in any doubt.