Normally in 2013 most mother boards only support 32GB RAM max and Duall Channel or Single channel only and has only 4RAM slots unless you are using a mother board with tripple or quad channel memory support (6 or 8 RAM slots) they will support more than 32GB of RAM (normally these are mother boards for server CPU) (also you need 64Bit windows to be able to use more than 4GB of RAM 32Bit only uses 4GB of RAM no matter if you have more than 16 or 32GB of RAM installed) (64BIT windows supports at least 128GB max of RAM installed on any kind of mother board and virtual memory size support is massive supports more than 1TB)
If you want to use 8GB or more RAM then you need to install a 64BIt windows supports at least 128GB of RAM while 32Bit windows only supports 4GB RAM max