When I first started to use iTunes, it very much played well with other software applications running. Then, a few versions later, the playback began to suffer with iTunes running in any way other than on its own. A solution that I have is to fire up the Windows Task Manager, go to the Processes tab and find iTunes.exe in the list. The next thing is to right-click on this, select the Set Priority and change the setting to Above Normal. Windows will warn you about what you are doing but it usually doesn’t cause any other problem. Yes, it sounds a bit extreme but it always solves the playback problem.
So long as iTunes is merely playing music, all is well. However, when it starts ripping CD’s, it’s a wholly different matter. That is a CPU intensive operation and setting the process priority to Low is a very good idea. I recently got caught out by a default setting of ripping any music CD inserted into the PC and, at Above Normal priority, the PC got locked up. Eventually, I got things back under control and lowered the priority. Needless to say, iTunes will just list the contents of an inserted CD from now on. I have learnt my lesson; keeping the command line open to get at command line process tools would be a very good idea for the future, especially as I know where to find these on the web.