@gauranshkushwah you re not giving us a whole lot to work with here. Going by what you wrote, this sounds like either a bad hard drive or a bad OS. You will have to check and see if you can get into your computer's BIOS and see if it does recognize the HDD. If so, then it is possible that this is an OS issue and you may have to reinstall it.
Use this [document|35522] to fix your computer. It does address hardware, software and troubleshooting steps.