TableNinja says that I must "deactivate TableNinja" on an old computer.
Solution:
Your purchase code allows you to use TableNinja on up to two computers that you own at any given time. If you wish to install TableNinja on a third computer you will have to deactivate TableNinja on one of your other computers.
Note: If you reinstall Windows or format your hard-drive TableNinja will consider your computer to be a new, different computer.
If you have unlocked TableNinja on two or more computers in the past, you will be shown a popup asking you to deactivate TableNinja on one of your old computers. Select one of your old computers to deactivate TableNinja on using the drop down menu provided and click "Confirm". If you receive an error please contact customer support using the email address provided in the error message.