Windows xp sp3 on bootcamp sees only 2gb ram. However, in my several years using windows xp in my desktop machine, I've only seen 3,5gb ram, never less than that!
Am I doing something wrong or bootcamp limits the usable ram??
your pc uses BIOS firmware, Apple and some others use Extensible Firmware.
You probably have EFI32 (as do I) which is crippled, broken, old, came out before the whole "Windows on Mac" and only supports 1.9GB in Windows. just the way it is.
And try the dictionary, encyclopedia - you can find those and some that focus on tech terminology via Google, Bing. Wikipedia is a good start though.