Please tells us what OS, the brand and model numbers of your hardware and few other things like:
1. Was this a new install of the OS?
2. Was the system working and then stopped working?
3. Did this occur after you made some other hardware or software change
4. Anything else you can think of that might help us understand the issue.
Lacking the above I would say you do not have it properly attached to the MB, correctly selected as SATA or IDE and improperly powered from the PSU. Oh yeah also the drive is defective, the MB is defective, the PSU is defective. So here are a bunch of answers based on no useful information provided.