This is an aggressive power saving approach which makes the system feel sluggish and underpowered..
Who is affected
It only applies to Windows 7 / 8 / 8.1 X64 and X32 and only in systems using more than 2 physical CPU's and/or more than 2 "logical" cores - ie: Core i7's.
Core Parking is a feature of Windows 7 that is causing rare performance problems. I don't notice it on my home i7 / Win7 system but some people are getting microstutters and odd behavior in certain programs. Without the following " tweak" you may see CPU spiking in your programs and Windows Task Manager - some CPU cores will be "turned off" / "parked" depending on load and they will be dynamically turned on or off and dynamically loaded up or down as the system deems necessary - the scope for glitches / pops / clicks / dropouts etc.... in such an environment is simply enormous. To the best of my knowledge, there is no known "switch" to turn it off - no utility I am aware of to "tweak" it off.