Windows 7 is Microsoft’s premiere Desktop Operating System. Essentially the R2 release of the Vista Operating System, Windows 7 boosts many new features not available in Vista. When combined with Windows Server 2008 R2, business clients can take advantage of increased performance and new technologies like DirectAccess.
Two versions, Professional & Ultimate, of the Windows 7 Operating System will work efficiently with an office network as both have the ability to join an office domain.
Both Versions also include a new powerful feature: Windows XP Mode which allows older Windows XP Applications to run inside of your Windows 7 Desktop.
For additional reading please see the Windows 7 Website the C3SD blog posting regarding the Windows 7 release.