My new hp dv2700t laptop with Vista is making weird clicking sounds...almost like crunching (and sometimes rattling) sounds every 20-30 minutes, sometimes more or less. Could it just be the hard drive is noisy? Is Vista the problem?

Vista is an operating system so it itself will not make any sounds
if you shake the laptop can you hear a rattle? has anything become stuck in the fan that can be catching on the blades?

best thing to do if it still under warranty is take it back, have them check it out