Uninstall Unity including License Data

I am trying to Upgrade my unity pro licence to Android pro. My problem is if I click on enter Serial under help Unity crashes. I have uninstalled unity and reinstalled hoping to put in the new serial but the old one is still registered on the machine.

How do I remove the old license from the machine to make a clean install.

Thanks

Unity Support Sent this

1.Uninstall Unity 2.Delete this file:

  • Win: C:/Documents and Settings/All Users/Application Data/Pace Anti-Piracy/License Files
  • Mac: HD/Library/Application Support/PACE Anti-Piracy/License Files

    1. Restart
    2. Download Unity again from our website, since your original install might be corrupt. http://unity3d.com/unity/download
    3. Reinstall and test