my system usually has 3 hard drives but now windows can only see 2. When the system is starting it will only show 2 drives when there is 3 physical drives installed. when you start the system the system light is constantly on. How do I get my drive back.........

Have you gone into the BIOS and see if it is still listed? If you cannot, you may have had a total drive failure. Do you know the make of the drive? Manufactures somtimes have utilites to scan their drives.

As acklan says... See some of the links to tools listed in the pinned post at the top of this forum by the mighty Leurgy.

Unless you've had some sort of BIOS corruption if the drive was there yesterday and not here today I'd say it's sionara to your third drive. Sorry.