There are solutions

1. Start - > setup - > control panel - > management tool - > service
Stop all Oracle services.
2, start - > program - > Oracle-OraHome81-> Oracle Installation Products->
Universal Installer
Uninstall all Oracle products, but Universal Installer itself cannot be deleted
5. Run regedit, select HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE, and press del key to delete this entry.
6. Run regedit, select HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services, and scroll
This list removes all Oracle entries.
7. Run refedit
HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ Eventlog \ Application,
Delete all Oracle entries.
8. Start - > set - > control panel - > system - > advanced - > environment variable
Delete the Settings for Oracle in the environment variables CLASSPATH and PATH
9. Remove all Oracle groups and ICONS from the desktop, STARTUP (Startup) groups, and program menus
10. Delete the directory \Program Files\Oracle
11. Restart the computer and delete Oracle completely after restarting
12. Delete files related to Oracle. Select C:\Oracle, the default directory of Oracle
Delete the following text from the Windows 2000 directory (1 C:\WINNT)
Pieces ORACLE.ES70en, oradim73.INI, oradim80.INI, ES75en.ini, etc.
13. Delete the marked paragraph of [ORACLE] from the WIN.INI file if any
14. If necessary, delete DSN of all Oracle related ODBC
15. Delete the Oracle-related logs from the event viewer
Description:
If there are individual DLL files that cannot be deleted, ignore them, restart and start a new installation.
When installing, select a new directory, then, after installation and restart, the old directory and files can be deleted.