Help please
I tried to add memory to my cpu. It did not work so I put the original memory back and now when I turn my system on, it beeps at me about 3 times and my monitor screen is blank. I can't see anything on the screen. I thought that it may be my monitor so I tried it on another monitor and it did not work. Please help and let me know what is wrong or what needs to be checked next.
Thank you

Welcome to PCHF

You have either put the original memory back into the wrong slot or it isn't seated correctly. Also check that you didn't disturb anything else whilst you were in the case.