PC won’t power on

Hi, I’m writing for my friend who just moved her computer from one room to another and now it won?t power on. Have tried all the obvious things, but when you initially plug in the power cord, the green light in the back comes on for a split second and then goes off. This happens each time we try to check the cord. I have read the other posts, and since we don’t know much about computers, should we open up to see if something came loose? or is motherboard probably problem. Thanks