Yes, but knowing which items to drop..that is the question. drop the wrong items and you might find your net connection tanks, or xp won’t boot.
Very unlikely. With most of these startup configuration managers, you just uncheck something you think you don't need. If you find you needed it after all, just check it back on and reboot. It doesn't actually get removed till you do another step. Plus, most of that stuff is configuration related, so it's unlikely it would keep windows from booting, but even if it did, you should be able to log into Safe Mode and check it back on and you'll be fine.