For months now we've noticed a Microsoft process called WmiPrvSE.exe continually running on our PC (Win7 Professional). There was no apparent reason for this but it was consuming a steady 5% of CPU resources on a 4 core cpu. We did a lot of online research but could come up with no reason.
However, almost by accident, we discovered that if we stop CCleaner running in the background then the problem with WmiPrvSE goes away. I guess there must be some kind of permissioning conflict.