Oracle is really difficult to uninstall .... 1. Choose "start"> "Settings"> "Control Panel"> "Administrative Tools"> "services" to stop all Oracle services. 2. Start-> Program-> Oracle-OraHome81-> Oracle Installation Products-> Universal Installer, and click "Uninstall product"-"Expand All ", select all directories except "OraDb11g_home1" and delete them. Run regedit, select HKEY_LOCAL_MACHINE \ SOFTWARE \ ORACLE, and press del to Delete this entry. 6. Run regedit and select HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services. Scroll through the list and delete all Oracle entries (Keys starting with oracle or OraWeb ). 7. Run refedit, HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Eventlog \ Application to delete all Oracle entries. 8. Delete all keys prefixed with Ora, Oracle, Orcl, or EnumOra in the HKEY_CLASSES_ROOT directory. 9. Delete all keys starting with oracle in HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ MenuOrder \ Start Menu \ Programs. 10. Delete all keys containing Oracle except the Microsoft ODBC for Oracle registry key in HKEY_LOCAL_MACHINE \ SOFTWARE \ ODBC \ ODBCINST. INI. Www.2cto.com 11. My computer --> properties --> advanced --> environment variables, delete the Oracle settings in the environment variables CLASSPATH and PATH. 12. Delete all groups and icons related to Oracle from the desktop, STARTUP group, and program menu. 13. Delete All Oracle-related directories (if the directory cannot be deleted, restart the computer and delete it again) including: 1.c:\ Program file \ Oracle directory. 2. ORACLE_BASE directory (oracle installation directory ). 3. C: \ WINDOWS \ system32 \ config \ systemprofile \ Oracle directory. 4. C: \ Users \ Administrator \ Oracle or C: \ Documents and Settings \ Administrator \ Oracle directory. 5. C: \ Delete the following files in WINDOWS: ORACLE. INI, oradim73.INI, oradim80.INI, oraodbc. ini, and so on. 6. C: \ if the WINDOWS. ini file contains a [ORACLE] Tag segment, delete the segment. 14. If necessary, delete all Oracle-related ODBC DSN15 and go to the Event Viewer to delete Oracle-related logs. Note: if some DLL files cannot be deleted, ignore them, restart and start a new installation. select a new directory during installation. After the installation is completed and restarted, the old directory and files can be deleted. It's really hard to uninstall...