A. Delete the Oracle services: In the registry, go to \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services and delete everything that starts with “Oracle”
B. Remove other Oracle stuff from the registry: Go to \HKEY_LOCAL_MACHINE\SOFTWARE\ and delete the key ORACLE
C. Reboot
D. Delete all the Oracle software from the directories where you installed it
E. Delete the Oracle software inventory: Delete the directory C:\Program Files\Oracle. You must do this no matter where you installed your Oracle software - the Oracle installer automatically writes information here.
F. Delete all shortcuts from your Start menu.
G. Remove the Oracle directories from PATH Environment Variable.