SQL express automated backup not working - please help

To backup a SQLExpress database from task scheduler:

Create a batch file (BACKUPDB.CMD) that will execute a .sql command file to backup your database.

BACKUP.CMD contains:

sqlcmd -S servername -U username -P password -i c:\backups\sqlbackup.sql

The sqlbackup.sql file contains the T-SQL statements to run your backup.

SQLBACKUP.SQL contains:

USE mydatabase;

GO

BACKUP DATABASE mydatabase

TO DISK = 'c:\backups\mydatabase.bak'

WITH FORMAT,

MEDIANAME = 'SQLExpressBackup',

NAME = 'Full Backup of mydatabase';

GO