How do i know if my hard drive is bad?

just ask it if its good or bad through your computer case? haha
no just type in google"HDD health" ok you will find something.

HD Sentinel (DOS / Windows / Linux):
http://www.hdsentinel.com/

HDDScan for Windows:
http://hddscan.com/

Download and run "HD Tune" and "CrystalDisk Info" - both are good programs and will tell you a lot about your hard drives including health status.

use the hard drive diagnostic utility from your specific hard drive manufacturer. its free for download from their website, weather its WD, Seagate, Hitachi etc. every manufacturer has their own diagnostic util designed to properly test their drives.