If you have MindMapper 16, then you can upgrade to MindMapper 17 for free.

Upgrade Steps
1. Go to MindMapper purchase page and click Upgrade.
2. Select your item and click Add to basket. Upgrades from 16 to 17 are priced at $0.00.
3. You will be taken to current license verification page. You need the following information: license information and email address.
- License information is found in the email that was sent to you when you first purchased the software.
MindMapper 16 Professional / English Registration key-set:
Name: Mind Mapper
Serial No: 1234-12345-123456-123456789 - Email address is found in the Registration Information page that shows up when you first purchased the software.