Give more information.
Maker, Model, and approximate age of every part.
Whether the computer has ever worked too.
If it has worked, for how long did it work and did anything happen before it stopped working?
That should get the absolute basics out of the way.
A complete stab in the dark for a couple things you could try are:
1) Push harder on the RAM
2) Put the RAM in different slots and still do #1.