After running an upgrade installation of Toad from a previous version, executing Toad launches the old version instead of the new upgrade.
The latest version of Toad may have installed into a different directory that once belonged to an even older install of Toad.
e.g. The Quest Installer picked up the 'C:Program Files\Quest Software\Toad' folder instead of the 'C:\Program Files\Quest Software\Toad for Oracle' folder and installed the latest version there.
User may have chosen the "Client" install option instead of "Full" for their first attempt of installing the upgraded version.
Launch the Quest Installer by going to the Window's Start Menu | All Programs | Quest Software | Quest Installer | Quest Installer. Go to Uninstall a product. Click on Toad if it is listed. It'll show you some details including where Quest Installer believes Toad is installed. This may or may not be correct.
Use the Quest Installer to uninstall Toad for Oracle X.x. Once removed, check to see if you have any other installs of Toad by searching for Toad.exe. If you wish to install on top of the existing Toad.exe, launch the Toad installation and make sure the correct directories are specified. If the installer does not let you change directories, then you may need to uninstall the older versions of Toad.
User Files folder and QSAuth11.key file under C:\Program Files\Quest Software\Toad for Oracle folder may need to be preserved prior to uninstall.