Purusothaman's solution will work for you
http://www.oxwall.org/forum/topic/8015?page=1#post-39125 .
If you don't have the user whose password you remember, register the new user.
Then find this user in ow_base_user table in the database>> copy his encypted pass>>find your admin's user>>replace his pass with the one you have copied.
Once changes are done and saved>>use your admin's username and the pass of your new user to log in as admin.