Q: I have 18 downloads of TV shows or iTunes Extras that I don't need. How can I permanently delete them?

Every time I have to install new updates or reboot my computer, iTunes will open and the available downloads start downloading automatically. Every time it does this, I have to pause and delete all of the items. Most of the items are HD which my computer will not support. I have no use for them and yet the option to delete is only temporary. Is there any way that these particular items can be removed permanently? Each time the automatic downloads starts up, it freezes and locks up my computer until I'm able to stop the downloads.