I’ve been plagued by intermittent stuttering in iTunes playback on my work machine. Until today I lived with it, figuring it was just a bug or a problem with my machine. But today on a hunch I Googled the problem and found what appears to be the fix: switching to “Safe mode (waveout only)” in the Audio tab of the QuickTime preferences. This fix for stuttering iTunes for Windows playback comes courtesy of Technovia, where the comments also have some more advanced things to try, including the DMA settings on the hard drive.
I should note one caution: in my tests, I didn’t close iTunes before I changed the setting. After changing the setting, iTunes finished playing the song and then closed abruptly. After reopening, it has been stutter-free. I would suggest closing iTunes first as a general rule.