Soon, members of the college class of 2004 will be heading off to start their freshman year. Since the slowest processors sold today are more than adequate for nearly any use, you don't have to pay a lot of money for that computer. Linux is an alternative only for the dedicated techie.
Laptops are attractive for a variety of reasons.
You can take them to the library or to class, though taking notes on a computer is not universally accepted. Laptops fit better in cramped dorm rooms. But they remain more expensive than desktops and are easily stolen. Choosing Mac or Windows is simply a question of personal preference. Many schools offer wireless networking in some buildings, and some are equipping their entire campuses, indoors and out.