To find out which product version you are using, refer to the contract number of your software.

Netviewer version 5

Version 5 of Netviewer uses a six-digit session number and a five- or six-digit contract number.

Find your contract number as follows (click to enlarge):

Netviewer version 6

Version 6 of Netviewer uses a nine-digit session number and the contract number contains seven digits or begins with "VNR 20..."

You can find these numbers in the Netviewer customer portal my.netviewer.com under "My contracts."  (click to enlarge). The username is the user's e-mail address.