My seagate 500gb not showing when i start my computer



i have a 500 GB barracuda 7200.11 seagate hard disk, twice massaged to take a buckup of the hard disk after that it is not working i mean i can not see the drives. if any have the solution please let me know.

It would help if we know where you can't see it. Does it show up in Disk Manager? In Device Manager? Does the BIOS see it?

It may be broken, it may need to have the cables reseated, it may need to be reformatted. More detailed information would be useful.