Trust me, Windows uses more than 4GB. Here's a thread about my work laptop. I won't go into too much detail... but: The swap file is used in addition to, not in replacement of, RAM. It's a feature of OS design overall and Windows is invested in it. Through personal experiences and lots of reading (I have B.I.T. too), I can tell you the swap file is a good thing. The general advice is that it should be twice your RAM. But with 16GB RAM, a 25GB max size should be plenty.