Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
In the Spotlight preferences (System Preferences, Spotlight) you can just drag your hard drive into the "do not Spotlight" list box.
 
You could also edit your /etc/hostconfig file.

Change "SPOTLIGHT=-YES-" into... well.. duh....have a guess 😉
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.