NAV2013 System Requirement say:
The Microsoft Dynamics NAV 2013 Windows client runs on the following versions of Windows:
• Windows 8 Professional or Enterprise (32-bit or 64-bit editions).
• Windows 7 Professional, Enterprise, or Ultimate (32-bit or 64-bit editions).
• Windows Server 2012.
• Windows Server 2008 R2.
• Windows Server 2008 (32-bit or 64-bit editions).
On 64-bit editions of Windows, the Microsoft Dynamics NAV Windows client runs in WOW64 emulation mode.
Microsoft Dynamics NAV 2013 Server only runs on 64-bit editions of the following versions of Windows:
• Windows 8 Professional or Enterprise.
• Windows 7 Professional, Ultimate, or Enterprise.
• Windows Server 2012.
• Windows Server 2008 R2.
• Windows Server 2008.
• Windows Small Business Server 2008.
• Windows Small Business Server 2011
Microsoft Dynamics NAV 2013 Portal Framework for Microsoft SharePoint 2010 runs on the following versions of Windows:
• Windows Server 2012.
• Windows Server 2008 R2.
• Windows Server 2008 (64-bit editions only).