[HarryT]

Originally Posted by eschwartz

By default there are a whole bunch. If you are technically inclined enough to edit the Windows Services you can manually disable them, of course.
Which requires being above average.

iTunes for Windows: Background processes installed on Windows XP, Vista, and 7 (Apple Knowledge Base)



iTunes: Still slowing down Windows PCs after all these years

But not everybody experiences the performance issues you describe. I never have, and I've been running iTunes for goodness knows how many years on a whole range of different PCs.