Compaq Laptop 3000 won't totally boot
 

I had a problem with my laptop : Compaq 3015us so i took it apart ( I
did not need to all I needed was a new power supply), I am now trying
to put it back together but I cann't get it to start. I took it apart
including the cooler for the CPU and the RAM, I now put everything
back together as best I can but when I hook up the power supply all I
get is a long beeping sound and no image to the screen, the hardrive
is fine I tried it on another laptop, any ideas what I may have
forgotten I am prettty sure I hooked up everything.

What I have done to try to fix:
removed the harddrive, the ram, the CDRom and pluged in the power, all
I get is the fan spinning, a light comes on showing power but no
image to the screen, and it doesn't seem to pass that stage. I
depress the power button but nothing changes, this has no effect, any
ideas?

Thanks

DN