In support of my blog on Development and Virtualisation, below is a guide to the maximum supported memory configuration for the current range of Windows Operation Systems.
Windows Server 2008 (32-bit)
OS
|
Maximum Physical Memory
|
Hot Memory Support
|
Add
|
Replace
|
Web Edition
|
4GB
|
No
|
No
|
Standard
|
4GB
|
No
|
No
|
Enterprise
|
64GB
|
Yes
|
No
|
Datacenter
|
64GB
|
Yes
|
Yes
|
Windows Server 2008 (x64)
OS
|
Maximum Physical Memory
|
Hot Memory Support
|
Add
|
Replace
|
Web Edition
|
32GB
|
No
|
No
|
Standard
|
32GB
|
No
|
No
|
Enterprise
|
2048GB
|
Yes
|
No
|
Datacenter
|
2048GB
|
Yes
|
Yes
|
Itanium
|
2048*
|
Yes
|
Yes
|
* Uses IA64 RAM
Windows Server 2003 (32-bit)
OS
|
Maximum Physical Memory
|
Web Edition
|
2GB
|
Standard SP2
|
4GB
|
Standard R2
|
4GB
|
Enterprise SP2
|
64GB
|
Enterprise R2
|
64GB
|
Datacenter SP2
|
128GB*
|
Datacenter R2
|
128GB*
|
* Requires Intel PAE
Windows Server 2003 (x64)
OS
|
Maximum Physical Memory
|
Standard
|
32GB
|
Enterprise
|
2048GB
|
Datacenter
|
2048GB
|
Windows Vista (32-bit)
OS
|
Maximum Physical Memory
|
Home Basic
|
4GB
|
Home Premium
|
4GB
|
Business
|
4GB
|
Enterprise
|
4GB
|
Ultimate
|
4GB
|
Windows Vista (x64)
OS
|
Maximum Physical Memory
|
Home Basic
|
8GB
|
Home Premium
|
16GB
|
Business
|
128GB
|
Enterprise
|
128GB
|
Ultimate
|
128GB
|
Windows XP (32-bit)
OS
|
Maximum Physical Memory
|
Home
|
4GB
|
Professional
|
4GB
|
Media Center
|
4GB
|
Windows XP (x64)
OS
|
Maximum Physical Memory
|
Professional
|
128GB
|