Hi, I purchased a second hand computer and it was working before I picked up from my friends house. When I got it home and plugged it in, it would just make the sounds like it's booting, the lights blinked, it beeped, but my monitor kept saying that "the monitor is working properly - check the system". It sounds like it wants to come on but doesn't. It's not the monitor because I've used the monitor on another computer. I took it to someone to look at and he said he found a small lamp knob (you know, the ones you twist on the lamps). And he said I probably need a new motherboard or some other thing I can't remember. Can you help me?