|could be the hard drive itself, getting ready to kick the bucket. if it's only 10GB, i'm guessing this isn't new hardware...|
could also be your PSU, not giving enough power at boot to spin up the hard drive, so the system doesn't recognize it.
i would make a backup of all data on that drive ASAP.
a screeching could also just be a fan dying, but that would not explain the BIOS failing to recognize the HDD. is it a direct correlation between when the system screeches and when the system does not recognize the HDD?