Deminsion 1100 only beeps after attempting to upgrade RAM

Attempted to upgrade Ram from 256 to 1256 had it booted once with the 1 Gig Ram then I attempted to add 256 (to the 1 gig) all it does is beep. I have tried every combination of memory in banks along with original Ram in bank. Probably removed and change Ram at least 20 times per bank. Could I have ruined the banks on the motherboard because the Ram slides in very easy does not feel snug, as it did when putting it in the 1st time. If the motherboard needs to be replaced any suggestions? It is a Celeron about
14 months old.