This can happen when new Users are created on a multi-user computer. Simply reinstall Power Drawers under the currently-active user. When doing so, you must reinstall to the same folder that Power Drawers was previously installed. The Power Drawers installer will probably default to the previous install folder.

If there is only one User on the computer, you should first restart Windows and then reinstall Power Drawers if restarting Windows did not restore the Power Drawers taskbar icon.