The following support article is somewhat outdated. Where it refers to booting from an installation disc, you should boot from your recovery partition (if running 10.7 or later) by holding down the key combination command-R at the chime.
After restarting with the Command R function, I received the Mac OS X Utility screen with 4 topics:
1)Restore from Time Machine Backup,
2) Reinstall Mac OS X,
3) Get Help Online and
4) Disk Utility
Now, I'm very much a novice, so how do I boot from a recovery partition from this point? Thanks for your help.