Computer won't boot

Hi, I'm new.
I've built about 4 comp and I know my stuff. I'm gettin real experienced because all but one had problems with it from the first boot. ANyways, my sister bought a HP Pavillion 505n and now that it's past the warrenty, it wont boot. The LED in the front won't light up. The p/s led is on and the fans spin slowly right when I plug it in (the power button does nothing) I tried another p/s, reconnecting all the power cables, checking to see if the mobo is touching any metal, and nothing. I did notice that when I tried powering it on when my cdrw is not plugged in to the power, the LED on the front turns yellow (like standby I guess). I also noticed that the case fan does not move or anything. when I plug in the power cable with all the power to the right spots in the case, the p/s spins slowly, the case fan spins for 1 sec, and I get NO beep. Could someone please help me, I hope i was clear enough. Thanks.