When you bought Virtual Drumline, you received a serial number. Depending on how you bought VDL, your serial number appeared on a label either inside the DVD case, or within the inside flap of the "Getting Started Guide." If you purchased VDL as a direct download, your serial number was emailed to you from Tapspace.
If for some reason, you are having trouble locating your serial number and need it to reinstall the software, you may retrieve it by logging in to your Native Instruments user account and selecting Products, Serials, and Downloads. There, you will see a listing of any NI products you've registered.
Your serial number is a very important part of your license to use the product, so we encourage you to keep it safe. It's also very important that you register your software right away, which will help us in retrieving your serial number should you accidentally misplace it. Lost serial numbers that haven't been registered are not recoverable.