Number of virtual processors in Hyper-V Guest Operating Systems

Article on Microsoft Tech Net with the latest information for the supported number of virtual processors and integration services when running different guest operating systems (virtual machines) on Windows Server 2008 R2 Hyper-v

http://technet.microsoft.com/en-us/library/cc794868(WS.10).aspx

Quick data

Windows Server 2008 (all versions, including R2 and SP1) - 1,2,3 or 4 Virtual processors (vCPU)

Windows Server 2003 (all versions, inluding R2) - 1 or 2 virtual processors

Windows 2000 Server with Service Pack 4 - only one (1) virtual processor

Windows 7 all versions including SP1 - 1,2,3 or 4 virtual processors

Windows Vista - 1 or 2 vCPUs

Windows XP SP3 - 1 or 2 vCPUs

Windows XP SP2 - 1 vCPU only, Windows XP x64 Edition with SP2  - 1 or 2 virtual processors