Clean Up Oracle

It is the first time I use Oracle for my work, and the version is 9i.
However, there was a problem for my first time installation, so I just uninstalled the program and tried to reinstall it, and the problem came.
Because I didnt drop existing databases first before uninstalling Oracle, when I reinstalled it and tried to create global database and SID, an error saying that "SID already exists..", as there are so many services running in windows after Oracle had been installed, even it was removed later, the services were somehow still running in the back-end, and there were some files in the directory that could not be removed!
To totally clean up previous install, there are certain things to do and the most important is to remove the registry entries for corresponding services, including:

HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE
HKEY_LOCAL_MACHINE/SYSTEM
----Controlset001/services/%oracle_services%
----Controlset002/services/%oracle_services%

HKEY_LOCAL_MACHINE/SYSTEM/
----Controlset001/ENUM/Root/Legacy%Oracle_services%
----Controlset002/ENUM/Root/Legacy%Oracle_services%

Note that to delete the entries in ENUM under SYSTEM directory, we need log into the system as administrator so that to get the permission.