Laptop wont boot. My Samsung XO5 laptop wont boot---I get message "operating system not found".

Question

My Samsung XO5 laptop wont boot---I get message "operating system not found". However I have discovered that removing the hard drive and just rubbing it and the ribbon cable often cures the problem----but it will surface again virtually every other day. My hard drive is new and replaced a three year old one which manifested the exact same fault----so it cannot be a hard drive problem. Can anyone help? This recurring fault is driving me up the walls.
John