Just to expand a bit on mlga91's comments, your motherboard will have a maximum memory limit based on it's own chipset (memory controller) and the number of memory slots it has. Additionally, you may have noticed that some operating systems (OS) come in 32-bit and 64-bit flavors. Regardless of what the motherboard can accept, a 32-bit operating system can only address up to 4GB total of memory. 64-bit operating systems can theoretically handle much more memory, but current operating systems cannot utilize more than 64 or 128GB of RAM (not sure which). Of course, most systems do not require more than 8GB or 16GB of RAM installed.
-Wolf sends