Every now and again my internet cuts out, if I have iTunes running at the same time it sometimes starts stuttering. Right clicking the network connection and doing "Repair" fixes my internet connection and then iTunes stops stuttering.
It's rare, and it never does it during normal internet use for me.
I had tried every suggestion I could find on google to fix the stuttering apart from re-installing Windows XP until I found a solution that works for me. Maybe it will work for you.
I've got Windows XP Service Pack 3, 2 gigs of ram and it was stuttering badly.
To fix this all I had to do was go to Task Manager by pressing ctrl-alt-del, right click on iTunes.exe under the Processes tab and set priority to Above Normal.
You will have to do this every time you use it unless you create a .bat file to make it happen automatically.
This is how I created the bat file (below). You will need to change the bit after "abovenormal" to wherever you have saved iTunes. Mine is saved on my P drive in the itunes folder, but yours will be saved somewhere else.
I opened Notepad and typed the following:
start /abovenormal p:/itunes/itunes.exe
Then Save As itunesloader.bat
Now all you have to do is double-click on that bat file to open iTunes in above normal priority mode every time.