Pagefiles make use of your harddrive to store some of the load from applications away from Ram. If you turn off the pagefile then your harddrive wont need to be accessed at all for files in use which means you get full use out of ram (which is accessed WAY faster) and that means that your computer will run faster overall but more of your ram will be used. Do it.
Microsoft doesn't allow that because of driver incompatibility(mostly display card), which will crush your os off. Windows Server doesn't use display card for 3D(most server display cards have 32MB RAM and not WDDM compatible), so with some(or no) tweak it can be used without problem. But most normal Windows user uses it for 3D gaming or at least Aero Glass in Vista/7, when Windows try to map it above 2^32 Address point, it will crush your system. I don't see why people argue about 32bit OS not being able to use more than 3.xGB of RAM when 64bit OS is out there with higher performance. Windows 64bit uses more RAM, of course, but who cares, since people who argue about this have their PCs with 4GB or more RAM.
Actually that's completely untrue. Obviously no OS will force a device to map to an address space that it can't use. And you can bet that at least every device which has 64-bit drivers can handle physical addresses above 4GB in its 32-bit drivers also. And this has been a requirement for WHQL certification for too long now. And performance gains have been doubtful in every benchmark thus far, while incompatibilities and lack of 64-bit apps are very real.
Then I'll be "that other guy" . PAE increases address lines from 32 to 36, so max memory is 2^36 = 64GB. But there's a catch. OS also has to support it. On microsoft systems only server OS' support PAE in this way. This was done since that increse didn't come free, program compatibility is reduced while PAE is active, although on server systems this usually isn't a problem since they run limited variety of software, and since that software is meant for servers they are prepared for PAE.
Do you actually claim that Microsoft shipped highly incompatible and unstable server editions? And nobody had a problem with that because they run very few applications on those servers? Do you people have any idea what you are talking about? PAE makes absolutely no difference to applications, only to kernel mode code which has to deal with physical memory.
And BTW, every Windows edition since XP SP2 uses a PAE kernel by default, to support data execution prevention. You can use a 4GB-only kernel if you specifically disable DEP in boot options. And if you do that, then I guess your system will be more "compatible"
I would suggest you to check on your sources. Nobody forces you to use PAE with 32bit server editions, but if you choose to use it don't expect everything will run as without it. And nobody said that it makes server editions unstable. Servers are written with PAE taken into account, that isn't guaranteed for every application that can be used on that server. Some analogy can be made with 64bit vs 32bit editions, most programs run fine under 64bit, but that doesn't mean that every single one will. On XP SP2 PAE is used because XD feature that DEP uses is in bit 63, and PAE is used only to allow access to that. It doesn't allow XP to address more than 4GB of RAM.