Again, it's not a bug but how computer architecture works. It's as simple as that.
Well you clearly don't understand how memory works then. It's a known fact that 32bit OS has a limit on virtual address space and just because you read what the task manager say doesn't mean you understand the whole story of memory.
I just checked Rage on Win XP 32-bit and the 1.2 patch fixed the 32-bit only "large texture cache" issue. No doubt soon the Skyrim High Res Pack issue will be fixed for XP 32-bit and glorious awesomeness of 32-bit WinXP (over newfangled upstarts) will be proven yet again! Check back here for "told you so post".
PS: You guys must be video driver technical experts at ATI/NVidia or something. I guess my Ph.D. in Computer Science, Windows (Nt/2k..) project experience at Microsoft and software engineering experience are no match for your awesome knowledge and skills!