Windows explorer or harddrive failure?

Hello I have a toshiba satellite laptop that was preinstalled with windows vista home premium. It has been working fine up until yesterday. Everytime I login to the home screen some weird sound comes from the harddrive and my computer freezes. It doesn't shutoff or display an error message it just freezes but I can still move my mouse icon, and that sound keeps coming from the harddrive. All I can do is forceshut down and when I start it, it does it all over again. I've tried running diagnostics and it still does it. Also the sound from the harddrive has happened before where it would freeze and usually keep running fine after a minute or two, or sometimes crash and restart. But this is the first time it has froze with that sound every time I start the computer. I have an essay due soon and this is really freaking me out and some good help would be appreciated