Unfortunately, I do not know of any way to do this. Visit the postgresql
website for more information.
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.