How to remove Oracle Database from your computer---By Roger Gong

To remove all Oracle components from a computer on Windows NT, Windows 2000, and Windows XP:
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Caution:
These instructions remove all Oracle components, services, and registry entries from your computer. In addition, any database files under ORACLE_BASE/oradata/DB_NAME are also removed. Exercise extreme care when removing registry entries. Removing incorrect entries can break your system.
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(1)Ensure that you first follow the instructions in "Stopping Oracle Services on Windows Platforms".
(2)Start the registry at the MS-DOS command prompt:
C:/> regedt32
(3)Go to HKEY_CLASSES_ROOT.
Delete any key that starts with Oracle, ORA, or ORCL.
(4)Go to HKEY_LOCAL_MACHINE/SOFTWARE.
Delete the ORACLE and Apache Group keys.
(5)Go to HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services.
Delete all keys under here that begin with ORACLE.
(6)Go to HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services /Eventlog/Application.
Delete all keys under here that begin with ORACLE.
(7)Go to HKEY_CURRENT_USER.
Delete ORACLE.
(8)Go to HKEY_CURRENT_USER/SOFTWARE/ORACLE.
Delete keys that start with Oracle or ORCL (if any exist).
Delete any Oracle keys (if any exist).
Close the registry.
Restart your computer.
(9)Update the System Variable Path
Go to Start > Settings > Control Panel > System > Environment tab.
Choose the system variable path and modify the Path variable.
Remove any Oracle entries from the path. For example, if JRE was installed by Oracle, remove the %ORACLE_HOME%/BIN path and the JRE path. You may see a path similar to this one:
C:/oracle/ora81/bin;C:/program files/oracle/jre/1.1.7/bin
Exit the Control Panel.
(10)Remove Oracle from the Start Menu
Go to SYSTEM_DRIVE:/winnt/profiles/all users/start menu/programs.
Delete the following icons:
Oracle - HOME_NAME
Oracle Installation Products
where HOME_NAME is the previous Oracle home name.
Delete SYSTEM_DRIVE:/program files/oracle through Windows Explorer.
Delete all ORACLE_BASE directories on your hard drive.
Restart your computer.