Computers for college?

I am heading to college in September of this year and the college I am going to has just sent out the reccomended specs for computers. My current computer, sadly, does not fill these recommendations. So does anyone know an affordable computer with the following specs? 2.4 GHz or faster processor 4 GB RAM minimum Windows 7 OS Windows XP is not supported through our Help Desk nor allowed on the wireless network 120 GB Hard Drive or larger CD/DVD Drive 802.11n Wireless LAN