The 32 bit version is available here.
The 64 bit version here.
Note: SP1 is a prerequisite for installing SP2.
More info (from Microsoft site):
Service Pack 2 for Windows Server 2008 and Windows Vista (SP2) is an update to Windows Vista and Windows Server 2008 that supports new kinds of hardware and emerging hardware standards, and includes all updates delivered since SP1. SP2 simplifies administration by enabling IT administrators to deploy and support a single service pack for clients and servers. Please see the Windows Server SP2/Windows Vista SP2 page on TechNet/MSDN for additional details and documentation.
Windows Vista SP2 TechNet
Windows Server 2008 SP2 TechNet
SP2 is an update to Windows Server 2008 and Windows Vista that incorporates improvements discovered through automated feedback, as well as updates that have been delivered since SP1. By providing these fixes integrated into a single service pack for both client and server, Microsoft provides a single high-quality update that minimizes deployment and testing complexity for customers.
Service Pack 1 is a prerequisite for installing Service Pack 2. Please make sure that your system is running Service Pack 1 before you install Service Pack 2.
Note: Windows Server 2008 released with Service Pack 1 included. Windows Vista SP1 information and downloads can be found on the Windows Vista SP1 TechNet page.
Windows Server 2008 SP2 and Windows Vista Service Pack 2 – Five Language Standalone version can be installed on systems with any of the following language versions: English, French, German, Japanese, or Spanish.
If your system has additional languages please use the All Language Standalone to install SP2.