I saw some Toshiba laptops advertised cheap for back to school. $649 or so with 3gb ram, pentium dual processor, vista home premium, etc... I think HP's are rated really well nowadays too. I've had Dells for the past ten years or so and haven't had any problems with them to speak of.

Or you could get a MAC but it would cost quite a bit more I think.

With Windows Vista, you'll likely need to get a new printer, etc... It doesn't work well with many older peripherals.