Recently my Xbox 360 hard drive began making loud noises and running very slow, I haven't diagnosed the issue as I'm not sure what it is, if it's bad sectors or if the drive is at the end of it's life. I haven't been receiving any error messages on my console so I wonder if it's something that can be repaired. Last time I turned on my console with the HDD in it the drive showed as "unformatted" with tons of data on it
If you can still access the data on the hard drive I would back it up ASAP, hard drives do eventually fail and it sounds like that is what is happening here.