...force it to use the pagefile memory instead of physical ram? Believe it or not, 4gb doesn't seem to be enough for this game lol. My computer just randomly turns off, and I know that it's because of my "low" memory capacity because the longer you play this game it gradually uses more and more memory according to task manager. So yeah, any ideas? (might resort to a memory upgrade, but would cost me alot more due to my motherboards 4gb limitation :/ )

It may be that you have a memory leak issue. I have 4gb of RAM and the game plays fine, and the amount of memory it uses doesn't ever seem to get past 1gb.

Not sure how you'd fix such a problem, but Google's your friend.
End some useless processes or something with task manager.

Turn your virtual memory setting up to like 8gb. But be warned, virtual memory is more than a thousand times slower than physical memory.

It definitely sounds like a memory leak, you should talk to BF3 support and make sure all your drivers are up to date.