<p>Under Windows Server 2003, Enterprise Edition, SP2 (/3GB switch not enabled)</p>

<p>As I understand it, and I may be wrong, the maximum addressable memory for a process is 4GB. </p>

<p>Is that 2GB of private bytes and 2GB of virtual bytes? </p>

<p>Do you get "out of memory" errors when the private byte limit or virtual byte limit is reached?</p>

Mark Russinovich started a series of posts on this..
Pushing the Limits of Windows: Physical Memory
While 4GB is the licensed limit for 32-bit client SKUs, the effective limit is actually lower and dependent on the system's chipset and connected devices. The reason is that the physical address map includes not only RAM, but device memory as well, and x86 and x64 systems map all device memory below the 4GB address boundary to remain compatible with 32-bit operating systems that don't know how to handle addresses larger than 4GB. If a system has 4GB RAM and devices, like video, audio and network adapters, that implement windows into their device memory that sum to 500MB, 500MB of the 4GB of RAM will reside above the 4GB address boundary.