You don't need any sort of computer, there are plenty of computer clusters on all sites. Sure it'd be nice to have one in your room, but it's perfectly possible to survive without. As for laptop/desktop - it really doesn't matter - there's not anything that you're going to need the portability of a laptop for, so it's just a personal preference thing. So sure, take your desktop for starters, and then, come November, if you think you'd like to get a laptop, get one.