If you no longer need Tableau Desktop or Tableau Prep Builder on a computer or you want to move it to another computer, deactivate the product key before you uninstall Tableau or you may not have the license available to activate on another computer.

You can activate Tableau Desktop on up to two different computers if they are used by the same person and one computer per user for Tableau Prep Builder.

1. Start the application on the computer where you originally installed Tableau.
2. Select Help > Manage Product Keys.
3. In the Manage Product Keys dialog box, select the product key and click Deactivate.
4. Close and uninstall the application.
5. If you just want to uninstall the application, you're done. If you're moving the application to another computer, keep going.
6. If Tableau Desktop isn't already installed on your new computer you can requst it from the Service Catalog. 

Instructions from Tableau Here.