Try the following steps to remove oracle completely….
1. Uninstall all Oracle components using the Oracle Universal Installer (OUI).
2. Delete the HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE key which contains registry entries for all Oracle products by using regedit.
3. Delete any references to Oracle services/components in the following registry location: HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/. Looks for key entries that starts with “Ora” which are obviously related to Oracle.
4. Reboot now
5. Delete the ORACLE_BASE directory. (i.e DriveLettter:\Oracle>)
6. Delete the DriveLetter:\Program Files\Oracle directory. (where u install most if that C:\)
7. Empty the temp directory.
8. Empty the recycle bin.
Now again reboot !
This can be used from the command line to remove the service:
<pre>sc delete OracleDBConsoleORCL </pre>