How to uninstall oracle step by step in Windows nt: 1. Start-> set-> Control Panel-> Administrative Tools-> stop all Oracle services. 2. Start-> Program-> Oracle-OraHome9i-> Oracle Installation Products-> Universal Installer uninstalls all Oracle Products, but the Universal Installer itself cannot be deleted. 3. Run regedit, select HKEY_LOCAL_MACHINE \ SOFTWARE \ ORACLE and press del to Delete this entry. 4. Run regedit and select HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services. Scroll through the list and delete all Oracle entries. 5. Run refedit, HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Eventlog \ Application to delete all Oracle entries. 6. Delete C: \ Program Files \ Oracle directory 7. restart the computer to delete the Oracle directory 8. Delete Oracle-related Files, select the Oracle Directory D: \ Oracle, and delete the Directory and all subdirectories. NOTE: If some DLL files cannot be deleted, You can restart and start a new installation. If you select a new directory during installation, after the installation is completed and restarted, the old directories and files can be deleted.