Uninstall the Oracle from the Windows Environment:
1. Uninstall all Oracle components using the Oracle Universal Installer (OUI).
2. Run regedit.exe and delete the folder HKEY_LOCAL_MACHINE/SOFTWARE/Oracle.
3. If you are running 64-bit Windows, you should also delete the folder HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/Oracle
4. Delete all references folder registry (HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/Ora*) (Note: Only relate to Oracle)
5. Reboot your machine.
6. Delete the “C:\Oracle” directory, or whatever directory is your ORACLE_BASE.
7. Delete the “C:\Program Files\Oracle” directory.
8. If you are running 64-bit Wiindows, you should also delete the “C:\Program Files (x86)\Oracle” directory.
9. Empty the contents of your “C:\temp” directory.
10. Empty your recycle bin.