I keep forgetting this all the time, so I cut & paste the necessary data in my blog so I will not where to look for it next time :-)

Note that the memory limits have changed between Windows Server 2003 RTM and SP1, especially for 64-bit support. The maximum physical memory is 1 terabyte for Enterprise and Datacenter SKUs.

 

From Memory Management: What Every Driver Writer Needs to Know:

The amount of virtual and physical memory that is supported on any computer that runs the Microsoft® Windows® operating system is determined by the hardware configuration and the edition of Windows in use. On 32-bit hardware, the virtual address space is 4 GB and the maximum amount of physical memory ranges from 4 to128 GB. On 64-bit hardware, the virtual address space is 16 terabytes and the maximum amount of memory ranges from 64 GB to 1 terabyte.

Table 1 lists the amount of virtual memory and the maximum amount of physical memory that each edition of Windows supports.

Table 1. Virtual and Physical Memory Support in Windows

Operating system version

Edition

Virtual memory

Maximum physical memory

Windows Server™ 2003 SP 1

Standard

4 GB

4 GB

Web

4 GB

2 GB

Enterprise

4 GB

64 GB, if hardware supports Physical Address Extension (PAE)

Enterprise (64-bit)

16 terabytes

1 terabyte

Datacenter

4 GB

128 GB, if hardware supports PAE

Datacenter (64-bit)

16 terabytes

1 terabyte

Windows Server 2003

Standard

4 GB

4 GB

Web

4 GB

2 GB

Enterprise

4 GB

32 GB, if hardware supports PAE

Enterprise (64-bit)

16 terabytes

64 GB

Datacenter

4 GB

128 GB, if hardware supports PAE

Datacenter (64-bit)

16 terabytes

512 GB

Windows XP

Home

4 GB

4 GB

Professional

4 GB

4 GB

64-bit Edition Version 2003

16 terabytes

128 GB

Windows 2000

Professional

4 GB

4 GB

Server

4 GB

4 GB

Advanced Server

4 GB

8 GB

Datacenter Server

4 GB

32 GB, if hardware supports PAE