No boot, no nuthin’!

Laptop would not boot-up at all. Installed new motherboard and Windows XP(used to be Home now Pro version), turn on power, light comes on, but that’s it. The same problem was happening as well before installing new motherboard. As I said, light comes on, no display, nothing. Does not seem like anything works at all except the light coming on to indicate power. Crazy! Any suggestions as to what could be the issue?