Migrating Windows server 2008 guests from Virtual Server to Hyper-V

Virtual server is limited to one CPU per VM. When you go to Hyper-V, it’s posible to use up to 4 virtual CPU inside each VM.

To be able to use more than one CPU you have to change from uni-processor hal to multiprocessor hal. So far I could research this change is not well documented for Windows Server 2008. Here it is:

Execute MSConfig, and then go to tab Boot -> Advanced Options…, check option “Detect Hal”, restart to these options take effect.

Or using command line:

bcdedit /set detecthal yes