I'd guess your Operating System is 32 bit, which limits your total RAM usage to just under 4GB. You can check in your System Properies if it's 32bit. To access the rest you'll need to install a 64bit OS.
I'd guess your Operating System is 32 bit, which limits your total RAM usage to just under 4GB. You can check in your System Properies if it's 32bit. To access the rest you'll need to install a 64bit OS.
The Windows key you already have will allow you to reinstall the OS in 64 bit. You would need to download the iso file for whatever OS you're on and then create a bootable disc or bootable USB and then install it by booting from the disc/USB in your BIOS.