Is your operating system is 64bit?
If you answered yes:
Search for an option for Memory Remapping in your bios.
If you answered no:
Get a 64bit OS.
If you answered I don't know:
Write dxdiag.exe in the search bar when you click on the start icon.
On the first page, in System information. Look for Operation system, it should tell you Windows Vista/7 32/64 bit.