Apple Mac Performa 640 series - Manual (Page 112)

How to install or reinstall Mac OS system software
You can install or reinstall system software by following the instructions in
the Macintosh Performa CD booklet that came with your computer.
If you’ve used Apple Backup to back up the contents of your hard disk, you
can use Apple Restore to reinstall system software. For instructions, see
“Restoring the Information on Your Hard Disk” in the section “Protecting the
Information on a Disk” in Chapter 4.
104 Chapter 7