All this is a misconception. Virtual memory is not hard disc space used as memory. It’s a virtual space described by adresses, neither in RAM nor in the hard discs, but virtual. Windows assigns pages of virtual memory to every program. If there’s enough physical RAM (as it should in most situations), the virtual memory will be assigned by Windows to physical RAM. Only if there’s no physical RAM left, will Windows assign virtual memory addresses to discs (pagefiles).
If you’re not short on physical RAM, hard discs won’t be used as memory, no matter how big your pagefile is.
Alternatively, if you were short on RAM, there would of course no way you could make the programs use physical RAM that’s already full, no matter your settings. Then it’s when the pagefile (which is simply a reserved space) must be big enough to fit everything that doesn’t fit in RAM. If it wasn’t big enough and Windows is set to manage virtual memory automatically, Windows will try to extend the pagefile–I’ve seen this happen at work. 88) If it wasn’t big enough and you prevent Windows from extending it, I bet you’ll have your Windows crashed catastrophically.
There’s no way you can make Windows (3.x and higher) use physical RAM directly. That belongs to the real mode of DOS days which I’m unsure modern processors will ever support, and believe me it sucked. Big. Time. Windows programs don’t know how to interface with RAM to start with, they just ask Windows for memory, virtual memory that is. If the physical RAM isn’t exhausted, they’ll be loaded there, no matter your settings.
People bitch a lot about Windows’ virtual memory without knowing what it is because of Microsoft’s Black Legend. They hear and believe that MS makes their computers work slower just for the heck of it. But it so happens that Linux uses the same device–of course, it would be a worthless OS if it addressed to real memory–, and what’s more it traditionally uses a whole partition instead of a pagefile, so it’s more difficult for the user to tweak it.
The ONLY effect of lowering the size of the pagefile is saving hard disc space, and risking a crash if you ever use a program that would not fit in your RAM plus pagefile along with the rest of the load. There is NO performance effect of tweaking the pagefile, period.
Since I’m no expert, please correct me where I’m wrong. Here’s some reference: