Startup Disk (System Preferences)

The Startup Disk panel of System Preferences appeared since first release of Mac OS X. Options related to the volume or disk to be used for starting up the Mac can be set here.

Various options
Users can choose from a list of available, bootable versions of Mac OS X and (if the hardware supports it) Mac OS 9. Alternatively, you can choose Network Startup.

If there is a whole lot of bootable folders to choose from, a horizontal scroll bar will appear.

If you wish to restart your Mac immediately, pick a volume in the list and click Restart... and confirm in the resulting dialog sheet.

If you wish to make your Mac an external hard drive and thus put it in Target Disk Mode, click the Target Disk Mode... button and confirm in the resulting dialog sheet.