My Dell xps L501x won't boot after replacing the Motherboard.

Hello;   I need ur help..  2 weeks ago I had problem with my dell ( the charger was turning off when plugged into the laptop). I called the costumer service and they said I should replace the Motherboard.. so I bought a new one and replaced it. and then  started the laptop ... The lights were on just for one second . I hold on the power 20 seconds an tried again to start it.. now I hear the hdd & cd driver working   but nothing else.( No lights ). Display is black.. nothing happens. What should I do? .. anyone can help? .Best r. Jimmy