Hello,
If you haven't already, please see the page on this site Product Info => Upgrading from 2.x or 3.0. This has all the information and instructions.
The $69 gets you an Advanced user license. If you don't want that, then you can purchase a basic user license for 3.6 at $34.
Then you will want to purchase the updated taxonomic lists for the areas you use (e.g. ABA and Clements). The taxonomic lists have the updated range info for the areas they cover.
3.6 works on Windows 7.
Let me know if I can assist further.
Jeff |