I've noticed that the computer slows down when iTunes is running, usually towards the end of one song and the beginning of the other.
Web pages take a while to load, changing active windows take a while to switch etc.
Could it just be the build of iTunes disagreeing with something?
It seems to be fine mid-song.
iTunes is installed onto my laptop, all my music (17.37 GB) is in one folder on an ext HDD.
I've defragged the laptop and the ext, aswell as done disk cleanup but to no avail.