"Some how the usable RAM is restricted to 4GB. Press Win+R to open a Run prompt and then execute the command msconfig. This will open the System Configuration. Click on the Boot tab and then Advanced options. The box Maximum memory should be unchecked to allow using the maximum installed memory. If this is not your case, next thing to try is boot into BIOS and see the RAM allocation for your onboard graphics card (if any). Keep it at 512MB or 1GB maximum, you won't notice any difference with more video memory."