Physical Memory Limits: Windows Server 2008
The following table specifies the limits on physical memory for Windows Server 2008. Limits greater than 4 GB for 32-bit Windows assume that PAE is enabled.
| Version | Limit in 32-bit Windows | Limit in 64-bit Windows |
| Windows Server 2008 Datacenter (full installation) | 64 GB | 2 TB |
| Windows Server 2008 Datacenter (Server Core installation) | 64 GB | 2 TB |
| Windows Server 2008 Enterprise | 64 GB | 2 TB |
| Windows Server 2008 HPC Edition | Not applicable | 128 GB |
| Windows Server 2008 Standard | 4 GB | 32 GB |
| Windows Server 2008 for Itanium-Based Systems | Not applicable | 2 TB |
| Windows Web Server 2008 | 4 GB | 32 GB |
Physical Memory Limits: Windows Vista
The following table specifies the limits on physical memory for Windows Vista.
| Version | Limit in 32-bit Windows | Limit in 64-bit Windows |
| Windows Vista Ultimate | 4 GB | 128 GB |
| Windows Vista Enterprise | 4 GB | 128 GB |
| Windows Vista Business | 4 GB | 128 GB |
| Windows Vista Home Premium | 4 GB | 16 GB |
| Windows Vista Home Basic | 4 GB | 8 GB |
| Windows Vista Starter | 1 GB | Not applicable |
Physical Memory Limits: Windows Home Server
Windows Home Server is available only in a 32-bit edition. The physical memory limit is 4 GB.
Physical Memory Limits: Windows Server 2003
The following table specifies the limits on physical memory for Windows Server 2003. Limits over 4 GB for 32-bit Windows assume that PAE is enabled.
| Version | Limit in 32-bit Windows | Limit in 64-bit Windows |
| Windows Server 2003 with Service Pack 2 (SP2), Datacenter Edition | 128 GB 64 GB with 4GT | 2 TB |
| Windows Server 2003 with Service Pack 2 (SP2), Enterprise Edition | 64 GB | 2 TB |
| Windows Storage Server 2003, Enterprise Edition | 8 GB | Not applicable |
| Windows Storage Server 2003 | 4 GB | Not applicable |
| Windows Server 2003 R2 Datacenter Edition Windows Server 2003 with Service Pack 1 (SP1), Datacenter Edition | 128 GB 16 GB with 4GT | 1 TB |
| Windows Server 2003 R2 Enterprise Edition Windows Server 2003 with Service Pack 1 (SP1), Enterprise Edition | 64 GB 16 GB with 4GT | 1 TB |
| Windows Server 2003 R2 Standard Edition Windows Server 2003, Standard Edition SP1 Windows Server 2003, Standard Edition SP2 | 4 GB | 32 GB |
| Windows Server 2003, Datacenter Edition | 128 GB 16 GB with 4GT | 512 GB |
| Windows Server 2003, Enterprise Edition | 32 GB 16 GB with 4GT | 64 GB |
| Windows Server 2003, Standard Edition | 4 GB | 16 GB |
| Windows Server 2003, Web Edition | 2 GB | Not applicable |
| Windows Small Business Server 2003 | 4 GB | Not applicable |
| Windows Compute Cluster Server 2003 | Not applicable | 32 GB |
Physical Memory Limits: Windows XP
The following table specifies the limits on physical memory for Windows XP.
| Version | Limit in 32-bit Windows | Limit in 64-bit Windows |
| Windows XP | 4 GB | 128 GB |
| Windows XP Starter Edition | 512 MB | Not applicable |
Physical Memory Limits: Windows 2000
The following table specifies the limits on physical memory for Windows 2000.
| Version | Limit in 32-bit Windows |
| Windows 2000 Professional | 4 GB |
| Windows 2000 Server | 4 GB |
| Windows 2000 Advanced Server | 8 GB |
| Windows 2000 Datacenter Server | 32 GB |
Kaynak , Microsoft MSDN : http://msdn.microsoft.com/en-gb/library/aa366778.aspx