Can you be a little bit more specific on your price? It'll make the difference whether to recommend a notebook or a netbook.
You can get a nice notebook for sub $500, however if you go much lower, you will see mostly netbooks.
H.D.D means hard drive disk capacity. This bigger this is, the more data you can store.
You may also check out education discounts. Just go to delluniversity.com, give them your student edu. email for verification, and you can get (I think) around 10% discount on some laptops.
Since you specifically asked for Dells, here are some. If you do the education discount, it'll be even cheaperhttp://www.dell.com/business/laptops?