first 64k memory failure, please help!!!

first 64k memory failure, please help!!!
i have a pc p4 2.4 GHz. 512 mb ddr ram pc 400 intel original 845 GLAD
from a few days my pc was getting this error first 64k memory failure
since then
the machine was unable to start, and gives three beeps
i tried to change the system memory without luck.
i think the problem should be in the motherboard as the base memory is on the motherboard itself
any help is highly appreciated.