There are loads of really cheap machines on dell outlet at the moment.
In answer to your question, all dell machines come with USB and network on board now. If you are buying from the dell outlet site I would strongly reccommend not getting a machine that has any version of Vista installed. There are very very few programs that are compatabile with it at the moment and the support is protically non existant as well for drivers (how windows talks to the hardware). There fore I would reccommend getting one with XP on, there are a lot of them on there around the £200 mark ex VAT and delivery.
Link to Dell Outlet: http://www1.euro.dell.com/content/pr...=uk&l=en&s=dfh
I have purchased a few machines now from the outlet site, and have been really impressed with them. 2 of the machines have been running 24/7 for nearly 2 years, with no problems what so ever. Also the machines are sooo quiet as well.
Oh and dont touch PC World with a barge pole. They are useless, as codprawn said.
If you need any more info then PM me and ill be happy to help.