Uninstall Oracle 11.2.0.1/12.2.0.1 On Windows
Prior to Oracle Database 11gR2, the Oracle Universal Installer was used to remove Oracle software from computers/servers.
Beginning with 11gR2, a new tool called the Deinstall tool was introduced and comes bundled with the Oracle Database Installation Software.
There are times when you must do a manual check to see all software and environment settings are properly deleted, such as partial failed installs which require a clean Windows environment prior to any reinstall attempts.
CAUTION:
1. These procedures will also remove Oracle network configuration files, in a specific ORACLE_HOME.
2. If there are user-written scripts and any other user-generated files in the ORACLE_HOME, they will also be deleted.
3. Exercise extreme caution when removing registry entries! Removing incorrect entries can severely corrupt your computer/server and may require re-installation of the Windows Operating System.
Please review the Steps To Deinstall Oracle From Windows guide attached.