Stopping Exchange for Backups

I am running Exchange Server 5.5 on a Dell PowerEdge 4300 with NT4 SBS 4.5, Backup Exec 7.3 with a SCSI DAT drive. I am experiencing intermittent I/O errors with my backup. It has been suggested that I shut down Exchange before scheduling the backup and then restart Exchange when the backup is complete. I was wondering if any one uses this method and is so if they could explain the proper procedure to follow to carry this out as a scheduled task. I am new to the position of network administrator. Thank You!

John