..... o1die is not entirely correct... if your running video editing programs like after effect cs5 that can use all the ram then the more the marrier. No u cannot use more then what your board says it will handle ... It more then likely would not post and possibly damage the ram and motherboard. DO NOT DO IT... If you want to use more ram swap mother boards.
Don't do anything stupid by exceeding your motherboard's maximum memory limit because i tried it in my old Pentium 4 computer and the motherboard got burned, when i took it in a computer service it said it might not be repaired at all. Maybe it was because
it was an old computer but i would not put my computer at stake. But the good news is that if your motherboard burns the hard drive will be ok but for the other parts i really don't know.