Click the link below and try the steps outlined there to remove all traces of Oracle, reboot, then reinstall:
If the problem persists after that, it is because of a CreateFileA conflict as I described above. Toad software licenses include 32 and 64 bit verisons. You, or whoever bought your license can download the 32 bit version here: https://support.quest.com/toad-for-oracle/13.3/download-new-releases