Currently Being ModeratedOct 12, 2012 9:21 PM (in response to JadieHarmony)
If it has Mac OS X 10.7 or newer installed, restart with the Option key held down and use the recovery partition. If not, you'll almost certainly need at least a Mac OS X disk to resolve the issue; occasionally, the internal hard drive will appear when pressing Option, and can then be booted from normally.
Currently Being ModeratedOct 12, 2012 9:33 PM (in response to JadieHarmony)
Except as noted above, no. This type of issue is usually caused by damage to the disk's directory structure, or damage to the Mac OS X installation, both of which require an alternate bootable system to fix, or the computer losing the ability to see the hard disk, which requires a hardware repair.
In rare cases, the computer may have lost the startup disk setting, which is fixable by the Option-key route described above followed by selecting it in the Startup Disk pane of System Preferences, or there may be a nonstandard cause which is indicative of a problem with a different component.
Currently Being ModeratedOct 12, 2012 9:57 PM (in response to JadieHarmony)
You can purchase a retail DVD which is newer than the Mac and use that. Note that in the event the OS needs to be reinstalled, that DVD won't install iLife unless otherwise noted. You may also be able to get replacement original disks by phoning Apple.