Scheduled Backup with MySQL Administrator on Windows
My God, this was tricky.
So, you set your backup job up, and just as you click on the schedule tick box, you get this weird message:
"You have to enable the Password Storage option on the programm's General Options tabsheet and select Obscured as password storage method to execute scheduled backups. Otherwise the backup task cannot log into the database."

Huh? What 'programms' Options? Ah. The button "Open options"! Do that, and go to "General Options", "Store Passwords" and "Obscured":

Now, just "Close" and get on with setting your scheduled job up.
When you "Save Project" the next hurdle comes along, with another confusing text:
"Enter user name and password for the account under which the task will be executed."

This is actually asking for the windows account the scheduled task will run under, not the MySQL account it should be using.
Also note that the command line for the scheduled job will make use of the stored connection you're using to set the job up - and each mysql connection is stored under the current windows user - so you better save the connection and set the job up on the MySQL and Windows accounts you will be using to run it under.
So, obvious once you worked your way thru it, as always...
Other points of interest:
- How connections are stored
http://dev.mysql.com/doc/administrator/en/mysql-gui-appendix-store-connections.html - The only documentation of MySQL Administrator Command Line parameters I've found:
http://bugs.mysql.com/bug.php?id=7843