I have an old laptop with an intel Celeron 560 and a spare core 2 duo t5600... so I tried to put the core 2 duo in the Celeron laptop, but it doesn't fit (I've checked both are PPGA478 on intel specification site). After further examination of the sockets, I see a little difference. So my question is what is the best CPU for my socket (and what I need to be careful about so it will fit) and why do the sockets have the same name but aren't fiscally the same.