This is something I've noticed.
BSD like Linux uses a "Swap Partition" on the hard drive to serve as slow RAM when you have to little memory to keep up with your computing. So it uses virtual memory
Windows has a Page file that seems to searve much the same purpose to my knolledge (intell would be nice). This paging memory likewise is supplimenting RAM.
When I run BSD, I use oh most no swap space and have many processes, According to my system monitor (I have 12 programs running counting system tray and task bar contents). My laptop (PCBSD) has around 150 processes going at this very moment with 0 Swap space used (checked in system monitor and swap space checking program). System is a AMD Mobile Sempron 3300+ (2Ghz/128KB L2 /w 512DDR)
At any given moment my desktop while running windows has about 50 processes (5-10 programs running between taskbar and systray) Task Manager shows that I'm usually using 100-250MB of my page file, over 500MB during a game. When I run PCBSD on the same desktop it has a simular load to my laptop and no swap use, Yet they both remain more responsive when launching/switching programs. under PCBSD then Windows. The desktop is a Pentium D (3.0Ghz/2MB L2 times 2 core /w 2GB DDR2).
My windows page file is setup as a 4GB file, performace favoring is windows defaults (favores using resources on user space if I recall).
I'm not a large fan of virtual/paging memory but is their any way I can try to make my Windows system as fast as my BSD ones ?