Blue screen of death frequently showing

Hi there,
I recently added a Ram Module to my HP pavilion Elite HPE then it started displaying the blue screen of death, I restored the Desktop back to defaults but am still getting this blue screen of death, I removed the new Ram module, restarted the computer, it worked well for a while then went back to displaying the blue screen of death, what could be the problem? What makes a computer to display this blue screen of death?
