@mikrev007: not exactly - it's true that no API allows an app to write to the page file directly (it requires SYSTEM authorizations, and all "Certified for Windows XP" apps are required to run in 'pure' user space, apart from services - so it's transparent). However, some apps try to allocate as much RAM as they can on load, and when page files are enabled Windows can report several Gb of space. So, if you have, say, 4 Gb of RAM with PF disabled, and the app tries to allocate 8 Gb, it may crash due to 'insufficient memory'.
Granted, this doesn't happen very often (even less with 12 Gb of RAM), but it's there.
However, Windows itself works better if it has a page file available, because it pre-allocates craploads of RAM to any app that starts, and also uses a lot of hard disk caching (as such, a lot of unneeded apps that get loaded in RAM are paged away to make room for said disk caching).
Through trial and error, I've found that installing your system fully, rebooting it and waiting for the harddisk to stop tharshing after boot, and THEN noting how much RAM is used, is a good starting point to evaluate your swap file size (if you have enough RAM to run even the most demanding app from RAM, obviously).
Case in point: reboot your system (fresh boot), open the Task Manager, and note how much RAM is used/allocated: let's say, Vista, an antivirus, and a few loaders, around 700 Mb. Then, open your System settings, Page file size: set a (fixed) size of 700-800 Mb (min and max). Reboot.
This way (if your system was not fragmented), you'll have a one-segment page file (it's faster to access) where the kernel can page away everything that is loaded at boot but usually unneeded, and you'll prevent Windows from swapping away running applications while not wasting 700 Mb of RAM space that'd be better off used as disk cache.
Or, you switch to Linux and you let a real RAM manager change your life