Dell Inspiron 530 does not boot up

Hi i have a dell inspiron 530 and I have a major problem  whenever I plug in my computer it comes on automatically the fans start spinning there is an amber light on the motherboard and the power led and I haven't even pressed the  power button yet. So far I have checked the power supply using the paper clip and it working . So I decided to check other components such as the ram, hard drive they work okay when I checked them on another computer .  So I narrowed it down to the power supply and the motherboard so I left the motherboard and the power supply connected with nothing else connected when I plugged in the power supply it came on automatically and the motherboard is not even connected to the power button . So thus far I have tried and tried and still don't know what the problem is.