Your PC's memory (RAM) is a very crucial component. If the RAM chip goes bad or develops too many errors your PC will start crashing, hanging and eventually become unusable until you replace the RAM. In many cases, a defective RAM module continues to work sometimes but causes sudden issues occasionally. This behaviour is very annoying as your PC can crash suddenly but it is hard to diagnose such a memory issue. Fortunately, Windows 8, Windows 7 and Vista ship with a built-in memory diagnostic tool. Let's see how to use it to know for sure if the memory is defective.