Maximum RAM supported by 64 bit editions of Windows:

* Windows XP: 128 GB
* Windows Server 2003 R2 Standard Edition: 32 GB
* Windows Server 2003 R2 Enterprise Edition: 1 TB
* Windows Server 2003 Enterprise Edition for Itanium: 1 TB
* Windows Server 2003 Datacenter x64 Edition: 1 TB
* Windows Server 2003 Datacenter Edition for Itanium: 1 TB