Hi,
If you still have the manual for the Asus motherboard it will tell you what the bios beep error code refers to.
I think three short beeps in a row if I remember relate to no memory detected, or it has failed in some way, have a check that the memory modules are firmly pressed into there slots and are the right way around, matching the key of the Dim slots.
Or it means the graphics card is not flush fitted in the Pci-e graphics card slot.
It`s one or the other so have a check.