Originally Posted by nvmywrx
Im sure you will need more info.
To help, we will most definitely need more info. Give us your current computer specs to start out with.
Do you have an OS currently installed on another hard drive in that computer?
Make sure you check your cables and confirm they are snugly connected to the hard drive because I have had this happen many times and 90% of the time it has been due to data or power cables that have shaken loose for whatever the reason. Also check the data connection to your motherboard.