Differences between Windows Server 2008, 2008 SP2 and 2008 R2

Windows Server 2008 and Windows Server 2008 SP2 are the same operating system, just at a different service pack level (Windows Server 2008 started at the SP1 level because it was released quite a bit after Windows Vista and SP1 ).

Windows Server 2008 R2 is the server release of Windows 7, so it's version 6.1 of the O.S.; it introduces quite a lot of new features, because it's actually a new release of the system. 


Windows Server 2008 R2 is includes key enhancements related to virtualization, management, IIS, scalability and reliability, and Windows 7 integration

There are also differences at the GUI level, because WS2008R2 uses the same new GUI introduced with Windows 7 (new taskbar, etc.).  

Depending on what kind of applications you're developing, they may or may not encounter problems on different O.S. releases; you should definitely check MSDN.

**Windows Server 2008 is the same codebase bits as Vista. It is available in two flavors 32 bit and 64 bit versions. 

**Windows Server 2008 R2 is the same codebase bits as Windows 7 x64. It is only available in the 64 bit version.

In Simple terms..

Windows Vista SP1 = Windows Server 2008
Windows Vista SP2 = Windows Server 2008 SP2
Windows 7 = Windows Server 2008 R2

please find the link below 

http://www.microsoft.com/windowsserver2008/en/us/whats-new.aspx.

http://technet.microsoft.com/en-us/library/dd335036(WS.10).aspx  ( windows 2008 SP2 )

http://www.microsoft.com/windowsserver2008/en/us/r2-compare-features.aspx ( windows 2008 R2 )
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Differences between Windows Server 2008, SP2, and R2

So what are the differences between win2k8, win2k8 SP2, and win2k8 R2? These naming conventions and differences between versions are a constant cause for confusion. So here's the short take:

Win2k8 was first released with SP1. Later on came Win2k8 SP2.

Win2k8 R2 is the new version of the OS that introduces several new features. It has the look and feel of Win7, it is only x64 bit, and Hyper-V Quick migration (~VMotion) is introduced.

There's no SP2 installed on top of win2k8 R2. R2 is a clean install or you can upgrade from SP2 to R2. In any case, the SP2 will disappear and it will only be called R2.

The reason for pointing this out is that it was a bit different with win2k3. Here, you installed SP2 and then you installed R2 on top of SP2 and the result was win2k3 SP2 R2 - so service pack and R2 at the same time.