Oracle completely uninstalled---window7 and window10 are personally tested
1 Right-click "Computer"-->Management-->Services and Applications-->Services, stop all Oracle-related services (start with Oracle, such as OracleDBConsoleorcl).
2 Start-->All Programs-->Oracle-->Oracle Installation Products-->Universal Installer, after the "Welcome" interface starts, uninstall the product-->Expand OraDb11g_home1-->Check Oracle Database 11g11.2.0.1.0-->Delete-->Select "Yes" in the confirmation window that pops up. After the uninstallation is complete, select "Close" in the pop-up "Product List" interface, and then select "Cancel" in the "Welcome" interface to exit the interface.
3 Start --> Enter regedit in the search bar to enter the registry
1) Select HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE, press the del key to delete this entry
2) Select HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services, scroll through this list, delete all Oracle entries (keys starting with oracle)
3）选择HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog\
Application, delete all Oracle entries.
4) Delete all keys prefixed with Ora or Oracle in the HKEY_CLASSES_ROOT directory.
4 Computer-->Properties-->Advanced System Settings-->Advanced-->Environment Variables, delete the settings related to Oracle in the environment variables CLASSPATH and PATH.
5 Delete all Oracle-related directories (if it cannot be deleted, restart the computer and then delete it), including:
1) C:\Program Files\Oracle directory.
2) Oracle installation directory, such as D:\app
3）C:\WINDOWS\system32\config\systemprofile\Oracle目录。
4) C:\Users\Username\Oracle