Dell Vostro 200 not turning on

Hello, today my Dell Vostro 200 refused to turn on, I opened up the case,  removed the PSU, and placed in a different one. It still didn't turn on, I put the original PSU back into the computer, and looked around the motherboard for any wires that were not plugged in, but I found nothing. Everything that needs to be plugged in is plugged in. The light on the back of the power supply lights up green, and there's an orange light on the motherboard. Also, the power button is lit up blue, but still does not turn the computer on. Any help would be appreciated greatly.