How to Uninstall all oracle clients installed in a machine

 • Stop Oracle service Using cmd 'net STOP service_name'

 • Uninstall all Oracle components using the Oracle Universal Installer (OUI).

 • Run regedit.exe and delete the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE key. This        contains registry entires for all Oracle products.

 • Delete any references to Oracle services left behind in the following part of the registry:           HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Ora* It should be pretty obvious      which ones relate to Oracle.

 • Reboot your machine.

 • Delete the "C:\Oracle" directory, or whatever directory is your ORACLE_BASE.

 • Delete the "C:\Program Files\Oracle" directory.

 • Empty the contents of your "C:\temp" directory.

 • Empty your recycle bin.