What is your platform & operating system version? Could it be you are running a 32-bit version of Windows?
i'm using windows 10, but I just checked and i do have a 32-bit operating system. Is there anyway way you know to change it?
Most likely your PC is a 32-bit system; I don't think your retailer sold you a 64-bit machine with a 32-bit OS. So I guess you can't change that, and I am certain you can't change it without at least buying a 64-bit OS and run that on a 64-bit machine.