Virtual memory has nothing WHATSOEVER to do with you present RAM in your computer. Virtual Memory is exactly what it says, Virtual, meaning it is not real. What your computer does, is it takes free space on your harddrive and allocates it as 'Fake' memory until either: A) You install stuff and take up the room on your HD, or B) you restart your computer.
To configure your virtual memory, although I would only do this if you are quite knowledgable in what you are doing, follow this:
Right lick on my computer, go to properties. On the tabs at the top, click Advanced, then click on the button for performance options. Now click on Change, where it says Virtual Memory. DO NOT change anything if you do not know EXACTLY what you are doing.