I just went through this with my son who's a freshman. To make a long story short, I finally convinced him that a more powerful and dependable desktop is way more preferable than a more expensive and fragile laptop that only offers less performance and greater headaches.
He ended up buying a great HP desktop with a Q6700, tons of memory, a video card and TV tuner for under $1000. He supplemented it with the cheapest Compaq laptop for well under $500 on clearance to add some convenience over the next 4 years should he need it.
Now that he's all set up at school, he's really happy with the desktop's performance and he also has a back up system in case he really needs one.
My older son who's a senior has had the same desktop going into his 4th year and has never had a laptop or wanted one, since they really aren't all that powerful for the money and don't provide the same degree of long term dependability.
When I was at the school bookstore last week, I talked to a student that bought a $1500 Toshiba that had a keyboard key break off after only a week of owning it and he was asking about having it repaired. The technician suggested to send it back for a full refund and then buy another laptop from the school store so he would be eligible for a backup laptop in case he needed a repair on it in the future.
My son's cheap Compaq appears to be even more durable than a Toshiba unit costing over 3 times more, and even if it wasn't, he has a beautiful performing desktop with a larger LCD monitor to rely on for years to come.
So the desktop unit is primary and the laptop unit is only supplemental.
Good luck with whatever you do decide to purchase.