smeezekitty :
The 4GiB memory limit is a marketing tool, not a technical limitation. Windows has supported more than 4GiB as early as Windows 2000 and Intel has supported it at the microprocessor level as early as 1995.
It
is a technical limitation.
2^32 = ~4GB of address space. This can be worked around using PAE but windows doesn't do that.
There is a good chance the game will "work" with less then 4gb but expect big lags if you dive into swap memory.
Anyone with a microprocessor of the Prescott architecture or newer is running a PAE kernel. PAE has been supported since Windows 2000 and is required to be enabled on architectures that have hardware enforced data execution prevention (DEP), which began with the aforementioned Prescott architecture. DEP cannot work without PAE as there is not enough space in the page table for the NX/XD bit without it. Windows XP shipped with both PAE and non-PAE kernels, and fully supported DEP as of SP2.
Microsoft disables memory remapping, not PAE.