My memory of a computer after the old shutdown

out to re-plug slots may not need a long time off the dust, clean look to try to re-plug the memory is not compatible! ! Normal problems! Only for the memory! ! Memory could not be added to some of the same model machine and even some of the same capacity to two different brands of memory can not use a piece of it, memory compatibility problems, look at the memory of the best brands and models to choose the same,