I am trying to install new memory into my desktop and when i put the new memory in, the pc won't boot. it turns on and i can hear the fan go but nothing else happens. I did a Crucial scan and used the recommended memory for my pc.

Its a dell xps 410 with an intel core duo processor. It has four memory slots with two 512mb currently installed. The pc runs fine with the old memory in but won't start with any of the new memory.