Bambi - Not all 32-bit systems are limited to 4GB of RAM. Linux with the PAE (Physical Address Extension) Kernel, can address up to 64GB of physical RAM. However, 32-bit addressing remains, so each virtual process in Proc is limited to 4GB apiece, though it can use 4GB 'blocks' in multiples.
The Linux current PAE kernel is a very easy install from the Distro's Repository, in a few clicks with the Synaptic (etc) installer. You then must reboot - a kernel change is one of the very rare things in Linux needing a reboot - installing / uninstalling multiple programs at once doesn't require rebooting.
I'm on a 3-months old PC, with Gigabyte GA-78LMT series board and 6-core AMD 2.8GHz CPU. So far has 8GB of DDR3, and 1 x 1TB SATA-2. I ran the Distro's (PCLOS - PCLinuxOS) default kernel initially, to get some data on performance. Then changed to the current PAE kernel.
For light-duties things, the difference isn't very noticeable - though when running even 6 light operations across 6 Desktops, the load now spreads more evenly across the cores - clearly visible in Gkrellm, the system functions indicator.
But with heavier loadings - video conversion with Avidemux, or Editing then Rendering with Kdenlive (like Vegas Pro) particularly on the Full HD 1920 x 1080 H264/MOV - either from my camera or the HD-TV 1440 x 1080 material, the difference is quite startling! About 45% faster.... And yes, I did have the data from pre-PAE to compare with... (Also, you can still reboot to the "old" kernel - just arrow-down at Boot Menu, and press Enter.)
Programs like Avidemux, Kdenlive, LiVES video editor, so on, have multi-threading options in Prefs - and that certainly helps load-spreading across the cores, too.
I usually use the Std HD with my camera - the 1280 x 720 - as that's slightly better quality H264/MOV (Fuji HS10 camera) - and an easier conversion to PAL 720 x 576 DVDs usable in TV-players. A lot of the TV here is in 1280 x 720, too, which for my purposes is convenient.
With the 1280 x 720 the PAE kernel improvement isn't as much as with the 1920 x 1080 - about 30-35%, which I call "a third" - and of course is much faster than the "lumpy" 1920 x 1080 overall.
Apparently Windows - XP, Vista, W7 - "could" use PAE kernels designed for those systems, to advantage, but the maker in its wisdom has chosen not to allow kernel changes at User/Desktop level. I'm told that NT-Servers do have optional PAE kernels, but can't confirm that - I've been out of the industry for some years. (I was a dealer level Windows tech and PC builder/repairer from Win-3.1, via the 9x years, to XP and start of Longhorn.)
Maybe with all the "new innovations" in Windows-8, one will be allowing PAE kernels - to be hoped, anyway...!