There are many tools out there that can do this job nicely but do you know that Microsoft actually comes with one as well that can do the same as many 3rd party tools? It’s called Windows Memory Diagnostic, and you can search for it in the Start menu to find it. Running a memory diagnose would be a good thing to do as the first step of your troubleshooting process. If your PC frequently freezes, reboots, or brings up a Blue Screen of Death, bad memory could just be the single cause of all these problems.
A defective memory stick could cause all sorts of problems to your computer.