>>However, when I try to create another DB with the same name I get an error that the name is in use by an existing DB.
Are you getting the error with the Configuration Assistant?
If so, you just need to go out and delete the FOLDERS that the config assistant created for you.
So if you created a db called FRED, go out and delete all the FRED folders. I believe they are located in the ORACLE_HOME directory.
Make sure that all entries in the registry are deleted.
1. From Dos prompt regedit- HKEY_LOCAL_MACHINE then SOFTWARE Delete all entries regarding to the deleted Database.
2. From Dos prompt regedit- HKEY_LOCAL_MACHINE then SYSTEM -CurrentControlSet- Services .Delete all the services about deleted database.