By design, when a backup set is deleted the Windows Scheduled Task should also be deleted. This is true if the Backup set is deleted from the source computer. However, if you delete the backup set from the Backup console on the storage computer, the Windows Task will not be deleted from the source computer.
To verify that all Windows Scheduled Task are removed, please go to the Source computer and click on the Start > Control Panel > Scheduled Tasks. Then remove all the Backup Tasks.
For the Vista operating system go to Start > Settings > Control Panel > Administrative Tools > Task Scheduler
Next open the Backup Console on the source computer and modify each Backup set to set a new scheduled backup time.