at the beginning of my boot, when i've just turned on my machine, the hard drive (i'm pretty sure it's the hd) makes very nasty sounding loud noises. it's like the normal activity noise but louder and more grindy. i dont like it. any idea what is causing it? corrupt boot sector or something? i hope nothing that drastic, but i am suspicious because it's only at the beginning of boot up as it is checking memory, and that stuff... advice appreciated as always.