I hate to be that guy, but I don't know anything about computers. I would love to research and learn about the components and choose my own parts once I get a firm grasp, but I'm in dire need of a new computer. It will just be used as a regular college student's computer. Microsoft Office, music/movies, internet, etc. I may use some engineering programs occasionally such as AutoCAD, Matlab, etc. My only real requirements are that the case looks semi attractive, pick up wireless internet, be able to connect to my Xbox for internet sharing, & DVD/CD burning capibility. Blu Ray would be nice if the budget allows. I might have left something out, so feel free to ask specific questions. The $500 is for the computer only. I have a stereo for speakers. I will however need a keyboard, mouse, and monitor. I will budget around $250 for that, so suggestions are welcome there as well.
As far as OS, I had a friend tell me that I should check out Linux, but I could really careless what OS I run. I don't mind learning Linux or a new OS, but I have been on XP since it came out and a user friendly system would be nice to start off with.
Again, sorry to be that guy that knows nothing and is surely asking simple questions with little to no detail.