I have bought Notezilla 7.0 first. Later I upgraded my Notezilla 7 to Notezilla 8. Then, I decided to use Notezilla 8 at home and use the older version at my office. However, I cannot register the Notezilla 7. When I registered Notezilla 7, the word --- "the activation key is invalid" came out. Does it mean that I cannot use my older version again??? Do I need to buy the activation key again?