Though I also suspect that you are dealing with a forgotten HOST or ADMIN password (it's been suggested but you have not yet confirmed that this is the case), there is another possiblity:

Older versions of DNN had a bug that sometimes caused password reminders for certain accounts to exclude the password for ANY user role, not just HOST or ADMIN.  When this bug affected an account it would consistently prevent the password from being included in reminder emails.

If your DNN version is 4.6.2 or newer then you are ok as far as that particular bug goes.

-mamlin

no they are saying look in the database table named portal you will see a colum named UserRegistration.

with this method you need to have access directly to the database to look at values and change values behind the scenes.

Lorddog

Any application that allows you to connect to a SQL Server database and manipulate the values within (e.g. Check out what Sebastian said).

If you are really stuck your hosting provider might help you here if they are feeling friendly (but you will probably need to tell them what to do if they don't know DNN very well), otherwise hire somebody.