Once SQL Server is installed and all windows are closed, the CPU usage never drops below 20% in VMM. I was puzzled by this for some time, probably longer than I should have been.

myResources for Windows lets you Monitor all PC resource usage in one graph. This gives you a clear idea on how each is performing right in one place. In task manager, you cannot see all graphs in ...

Joey on SQL Server Why Activity Monitor May Be Hurting Your SQL Server's Performance As Joey explains, Activity Monitor consumes a lot of resources and yields little usable data.