Pc is not working

I have a toshiba laptop, and i figured that the processor and one that i have sitting there share the same socket, and i read that if they have the same socket nothing wrong would happen if i change one for another (one being an athlon and the other one being phenom, in a chance of improving my pc performance) i changed the athlon for the phenom and i started the computer but only a blackscreen appeared, changed the cpu again, this time for the one that the pc came with, and nothing but blackscreen. i tried connecting a monitor but nothing happend either, what can i do? is my pc dead? thanks for the answer, and sorry for my english