XP/32 is theoretically the most capable of 4G memory, but it is virtually impossible to use full 4G memory. Microsoft's official claim is that Xp/vista 32bit allocates some of its memory to the memory address that is reserved for the device after installing 4G memory. Therefore, the system attributes can only see the 3G to 3.5G of memory capacity, the remainder is not useless, but the system is seized, users can not directly use. And the 32bit Xp/vista does not allow a single program to occupy more than 3G of memory, which is the characteristics of the system kernel.
If you want to support 4G memory, it is best to replace the operating system, XP 64-bit, Win 7 64-bit, or win 2003 (WIN 2003 is the server operating system) can well support 4G memory or larger capacity of memory. Although there are many patches on the internet can be cracked XP 32-bit memory limit, can show more than 4G of memory, but, after measured, most of the model of the crack, just a number game, that can only display, can not actually call.