I exactly have the same problem as you. Even when the VM is idle, CPU usage is over 100%. I have requested the support and the engineer was not able to solve the problem. He said it will be escalated to 2nd level engineers. Thare is no contact since that they, though.
What I have personally found out is when you look at the task manager you might see some services that particularly use high proportion of cpu. In my case, that was local service host ... something which is releated to p2p services. I turned off that service, and it made the cpu usage level about 80%. There was one more service, "werfault.exe". What this services does is when you have problems in windows system it reports the problems to the Microsoft. So I decided to turn it off as well, but right after I turned off werfault.exe, rundll32.exe error popped up. Turning off the werfault.exe made my cpu usage near 0% when idle, but because of rundll32.exe popping up every seconds, I was forced to turn it on again.
I have also googled the "werfault.exe" error, and found out the cause of this error is most likely related to the drivers, which indicates that there is something wrong with the PARALLELS TOOLS. Funny thing is it only happens in Windows 8.1. I tried Win 8 and Win 7, no high cpu usage was not detected.
Since there is lack of support from parallels team, I strongly encourage you downgrade your windows 8.1 to windows 8. I believe downgrade the OS will definitely solve your problem. It's quite funny that only some people have this high cpu usage thing happen, I don't expect the parallels support team would catch this problem and fix it in any soon. Huge disappointment this time to parallels. Will definitely change my VM to fusion next year
