If you guys regularly use Oracle Database 10g in your XP machine, then you’ll definitely realize that Oracle DB tends to leave shit lying in your system when you uninstall it. These remnants of the database installation will sometimes create problems with your XP system. Leftover registry keys will cause problems when you’re reinstalling Oracle DB. Leftover path variables sometimes wreak havoc on your normal command prompt utilities like ping and telnet. Leftover files and directories will make it harder to install a new database using the same Oracle Home name.

Before starting these procedures, go to Start > Run and type “services.msc”. Stop all Oracle-related services.

The first step would be to use the Oracle Universal Installer. This is usually located in Start > All Programs > Oracle - OraDB10g_home1 (or whatever your Oracle Home name is). Put a check in the Oracle Home name that you’d like to remove and click ‘Next’. When the uninstaller has finished removing the installation, exit it.

Next, open up Registry Editor. Click Start > Run and type “regedit”. Follow these steps:

• Go to HKEY_CLASSES_ROOT and delete keys that begin with Ora, Oracle, Orcl, or EnumOra.
• Go to HKEY_LOCAL_MACHINE\SOFTWARE and delete the ORACLE Group key.
• Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services and delete all keys under this branch that begin with Oracle.
• Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services \Eventlog\Application and delete all keys under this branch that begin with Oracle.
• Go to HKEY_CURRENT_USER and delete the ORACLE key.
• Go to HKEY_CURRENT_USER\Software and delete all Oracle keys, including Oracle-HOME_NAME entries under: Microsoft\Windows\CurrentVersion\Explorer\MenuOrder\Start Menu\Programs.

After you’ve finished editing the registry, reboot your computer.

Now we will ensure that your environment path variable is free of Oracle crap. Go to Control Panel > System > Advanced > Environment Variables. Remove any Oracle path lines in PATH.

And after that you can proceed to delete the Oracle directory and Start Menu entries.