reinstall WB
This is not required really. You can change the admin password directly to the DB. Use folloing query in your database to change it (change the table name to what you have):
UPDATE tableprefix_users set password = md5("new password") where username = "admin";
This changes the admin password to new password (without quotas).
You can also replace the username = "admin" with any other user whos password you wish to change.