That is pretty clear as well. If you are looking to reduce the number of vCPUs being utilized in your environment don’t expect a reboot to be all that is required to have the VM running in uniprocessor mode.
Forcing Windows 2008/2008 R2/7 to redetect and use an appropriate HAL for the number of vCPUs it has been allocated or has been changed is a pretty simple affair:
Execute MSConfig, and then go to tab Boot -> Advanced Options…, check option “Number of Processors”, change the number to # of vCPUs being utilized.
Or using command line: