HDD constantly being accessed

Can anyone help. I have an Asus X58 mobo, i7 950, GTX 460 and a WD Cav black 640gb connected to the Sata 6gb controller. All HDD BIOS settings are set to AHCI. The HDD is constantly being accessed making a low ripping sound, i dont know if this is normal but it seems a little loud and with it constantly being accessed, even when idle, its becoming very annoying. I've read about PCIE lane bandwidth allocation settings helping some and also enabling the RAID setting in bios has helped some people but i cant see how this would help me. I feel that it might need RMAing but i require advice 1st, especially with the problem of the HDD constantly being accessed all the time. I also require advice on how to update the Marvell BIOS version 1019 prior to a win 7 installation, i can update the drivers after installing win 7 but the Marvell BIOS stay at version 1019. Its a recent build and recent win 7 installation. Any advice, tweaks and performance tips would be greatly appreciated.