Why the hard noise during bootup?

My computer (Windows XP Home sp1) has just started making noise when I turn it on. It sounds like the hard drive is going up hill. As soon as the computer is finished loading the sound is still there. When I log in to my XP and bring up windows explorer the sound slows down and eventually I never hear another sound. This mostly happens when I do a cold start up or boot up. Is the hard drive getting ready to bite the dust? Please help. This computer is a new Dell 8200 w/256MB RAM