Hard drive crapping out?

one of my hard drives is making some weird noise every now and then... it's the noise it makes when i turn off the computer.. sort of sounds like it just lost power and turned off... is this a known sign of a hard drive crapping out? i want to make sure because i have tons of data that i dont want to lose.. thanks

Time to start backing up ...

okidoki, it is all backed up now i'm just waiting so i can have an excuse to buy a 120gig...