So the PC doesn't start at all? Several questions:
1. Do you see the small LED on the motherboard? It lights red or green?
2. When you put the hand on the PSU fan grill do you notice the air flow coming out of PSU?
3. Do you hear any beeps / warnings from mobo?
4. As I understood from your post, you don't seem to see the BIOS, right? So you don't see the POST screen displayed too, yes?