Laptop wont boot!

I have a Compaq Presario 1220 Laptop. It has a Cyrix 200mhz chip in it. It was locking up, so I thought I’d try another chip to help performance, and put a Intel Pentium 75 in it. From then on, it wouldnt boot. IT powers up, but nothing on the screen, I checked all the cables and everything is plugged in right and connected ok, and the old chip is back in, but not a thing on the screen when I press power. Not a battery issue, it’s plugged in and I see the power light come on, and hear the HD initialize… is it fried? Or did I forget something?