If you can handle it, simply and carefully flip the laptop over and remove the battery. Flip it back over and hold down the power button for 10 seconds to drain the power. Flip it back over and remove the cover over the hard drive, usually it`s the biggest cover. Confirm that the hard drive is fully seated. There are usually 2 or more screws holding the hard drive in place. If they are all in place and tight, chances are the hard drive is securely in place. Simply push on 1 end of the hard drive and make sure it`s firmly seated against it`s power and data connectors. There are many videos you can watch on youtube.
Use the right size phillips screw driver
and DON`T STRIP THEM..
If you have a warranty, send it in for repairs. DO NOT work on it yourself.