Hello,
My mother has an Compaq Presario that's a few years old. It's running Windows XP Pro. She called and said that the peripherals started working intermittently (monitor, keyboard, mouse), and now they don't work at all. She says that the PC turns on, but nothing else does. No lights on the keyboard, monitor doesn't come on.....

Does anyone know what the problem could be? I'm going to go over and try to fix it. I've done basic work on PC's like adding memory, drives... so I'm pretty comfortable "getting under the hood".
Thanks for any help.

First impression is a failed motherboard or faulty power supply.

Disconnect/remove everything but motherboard, CPU, memory, power supply, monitor and keyboard. If it still won't boot replace any components you can starting with power supply.

Let us know if there are any beeps on boot and whether the PC turns on at all (e.g. fans run, lights flash).

Thanks, I will try that and get back to you.