Unfortunately, I do not know of any way to do this. Visit the
postgresql website for more information.
6/16/2009 Update:
In order to log into PostgreSQL when you have forgotten the password, you must uninstall, delete the postgres user account, and then reinstall.
To remove the postgres user account:
Go to Start-->Run
Enter 'CMD' (without the quotes) and click OK
Type 'net user postgres /delete' (again, without the quotes)
If you get a operation failed message and are running Windows Vista, turn off User Account Control and try again.
