32 bit code / Windows and 4 GB of memory

From time to time, you would have a lot of queries about using a 32 bit of Windows along with a machine that has more than 4 GB of memory. Typically, most retailers will inform you that there is no point in having a machine that has more than 4 GB of RAM, since you will not get the benefit due to restrictions with the memory management of the OS.
Learn a lot more about the usage of memory in these areas (link)

Though machines with 4GB are not yet the typical purchase for home or business use, they are readily available from major manufacturers and it won’t be long before they are the typical purchase. But there are problems. You don’t have to stand for long in a computer shop to hear a sales assistant talk of 4GB as some sort of limit for 32-bit operating systems, and it won’t be long before this sales patter develops into outright promotion of 64-bit Windows as the only way to get past this limit.
That 32-bit editions of Windows Vista are limited to 4GB is not because of any technical constraint on 32-bit operating systems. The 32-bit editions of Windows Vista all contain code for using physical memory above 4GB. Microsoft just doesn’t license you to use that code. Well, to say it that way is perhaps to put words in Microsoft’s mouth. I say the restriction to 4GB is a licensing issue because that’s how Microsoft’s programmers evidently have thought of it. The 4GB limit is retrieved from the registry by calling a function named ZwQueryLicenseValue, which is itself called from an internal procedure which Microsoft’s published symbol files name as MxMemoryLicense. If you remove this check for the licensed memory limit then a restriction to 4GB is demonstrably not enforced by other means.