reset sql server to default?
To completely reset everything would involve uninstalling/reinstalling SQL Server.  But this is overkill.  Instead it sounds like you have two things you need to do.

Thing 1

First thing you should do is clean up your endpoints.  I would do this on both your primary and mirror server.  The DROP ENDPOINT command is straightforward.  If you need to see what endpoints are currently out there, you can select from sys.endpoints.

Thing 2

Drop your old database.  If it's stuck in recovery, the first thing to check is your SQL Error Log on the mirroring target and make sure it isn't actually doing anything.  You want to look for messages containing the word "Recovery" and "Step n of 3".  If these are there, it's still in the process of restoring.  Otherwise, you just need to complete the recovery with:

RESTORE DATABASE [foo] WITH RECOVERY;


Once you have completed recovery and the database is online, you should be able to drop it.