Since I upgraded my PC to Vista, iTunes had been skipping. Under XP on the same machine, iTunes had been playing OK. Playback would stutter/skip several times a minute. It was really annoying. I couldn’t find a fix anywhere, although all the fixes seemed to point to Quicktime or upgrading codecs. However my fix turned out to be something else. In Quicktime, I changed “Play audio using” from “Direct Sound” to “Windows Audio Session”. No more skipping! Apparently the “Windows Audio Session” option became available with iTunes 9.