Check in msconfig / Boot / Advanced Options. Maximum memory has to be unchecked.
Also in BIOS /Advanced Chipset settings / North Bridge, Remap Memory has to be enabled.
both of these are as they should be, still didn't fix the problem I think my bios is out dated but the only updates are for windows vista / windows 7 but im running windows 8 not sure if that has any cause to the problem
bios is not os depent it not a driver. the last bios file for your mb is Version 2202. if your bios is less that that download the file to a usb stick do into the bios and use the mb bios updater tool. if the memory still shows 4g you may have a bad memory stick or a dead ram slot. take out both dimms. try each dimm by itself. if you have a bad dimm them one of them wont read/system wont post. if you have a bad slot in the mb moving the dimm to another bank may work. the issue to is if the ram is 2 sided ram the mb may be only reading 1/2 the ram.