Memory Limits for Windows Releases

http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778%28v=vs.85%29.aspx#physical_memory_limits_windows_7

 

Physical Memory Limits: Windows Server 2008 R2

The following table specifies the limits on physical memory for Windows Server 2008 R2. Windows Server 2008 R2 is available only in 64-bit editions.

Version Limit on X64 Limit on IA64
Windows Server 2008 R2 Datacenter 2 TB
Windows Server 2008 R2 Enterprise 2 TB
Windows Server 2008 R2 for Itanium-Based Systems 2 TB
Windows Server 2008 R2 Foundation 8 GB
Windows Server 2008 R2 Standard 32 GB
Windows HPC Server 2008 R2 128 GB
Windows Web Server 2008 R2 32 GB