WORKAROUND:
Try installing with the msi installer instead of the exe. Both can be downloaded from the Support Portal.
Note, this does not guarantee there won't be other limited privilege conflicts with the installer. Using the msi may only help address some privilege limitations. If this continues to be an issue, please refer to your system admin and request that a user with full admin privileges run the installation of Toad.
Please refer to the most current version's release notes and installation guide online to verify permissions and installation steps.