Manually Uninstalling Oracle in Windows

• Uninstall all Oracle components using the Oracle Universal Installer (OUI).
• Run regedit and delete the HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE key. This contains registry entires for all Oracle products.
• Delete any references to Oracle services left behind in the following part of the registry (HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/Ora*). It should be pretty obvious which ones relate to Oracle.
• Reboot your machine.
• Delete the "C:\Oracle" directory, or whatever directory is your ORACLE_BASE.
• Delete the "C:\Program Files\Oracle" directory.
• Empty the contents of your "C:\temp" directory.