Two ways to skin this.
Buy a cheap machine in the $250 range that will run the MS Office suite. You can afford a new one for each of the 4 years.
Buy a higher end machine and hope it does not get lost,stolen, beer poured on it etc....
I'm a Mac fanboy, no secret there. The benefit of the Mac is you get a great piece of hardware that can run whatever operating system you want/need.
I'd shop the Apple refurb store. Inventory changes constantly so if you see a deal grab it, if not check daily and what you need will eventually pop up.
You want a light weight box that is not physically large and has good battery life. Although not a fan of the flash storage the Mac Airs are nice portable boxes.
Refurbished 13.3-inch MacBook Air 1.8GHz dual-core Intel Core i5 - Apple Store (U.S.)
Refurbished 11.6-inch MacBook Air 1.8GHz dual-core Intel Core i7 - Apple Store (U.S.)
Pick up any brand 22 in external display and mouse/keyboard combo for back in the dorm room.
Forget about a laptop for gaming, it's not something they do well unless you go for an Alienware rig which besides being a great machine is expensive, heavy, cumbersome and eats battery life.