If you’re running the latest version of Parallels on your Mac (version 3.0, build 4560), you might have noticed that when your Windows virtual machine is running, your Mac’s CPU is almost exactly 50% utilized even when Windows is idle. If you’re on a MacBook or MacBook Pro, you’ll notice this pretty quickly since your fan will be running basically non-stop.
So, what’s the culprit? Strangely, based on this forum thread it appears to be iTuneshelper.exe, a background process that is installed with the latest version of iTunes (7.3.1.3). You probably only have iTunes because you wanted Quicktime on your Windows instance. Most people running Windows as a virtual machine on a Mac have no need for iTunes’ ability to connect to an iPod, since iTunes will be available on the host OS X operating system for this purpose.
In that case, you can use the System Configuration Utility in Windows XP (click Start, Run, then type “msconfig” and press enter) to turn off the Apple Mobile Device and iPod Service under the Services tab by unchecking them. Apply and close out of MSConfig.
The next time you boot up, you will get a warning message that you are running in Diagnostic mode. Check off the box on this dialog to make your change permanent (you can always go back in to MSConfig and recheck the boxes if you need to).
Interestingly, this tweak may only bring Parallels’ CPU utilization down to around 20%. That’s much better, but a far cry from the 4 to 6% used by the previous version. Clearly the celebrated utility has taken a step backwards performance-wise, but nobody can argue with the convenience of being able to run Windows on your Mac at the same time.