Are you using a USB mouse and keyboard? If so, find yourself a PS2 keyboard so that you can go into BIOS and make sure that USB keyboard is enabled, if its not it wont work. Also, test the mouse and keyboard in a different system just to make sure they arent the bad parts.
You need to start a NEW thread for your situation.Ok but my mom bought a refurbished computer, the processor is a hp windows 7 and it came with a ubs ported mouse and keyboard. The monitor is a dell, it powered up completely fine and then the mouse and keyboard stopped working