help with high speed internet, wireless, media center, etc.

[Maengelito]

Okay folks, when it comes to anything computer related more than teh internetz, email and youtube, I'm mildly retarded. Jenn currently has comcast high speed internet and a wireless router. However, I just found out that she's paying like $3 a month to rent the cable modem. I figure after like a year, it'd pay for itself, so I want to pick up a cable modem. However, do they make cable modems with routers or wireless routers built in? Also, I'm going to be buying a friend's used laptop with wireless capability so eventually I'd like to turn my desktop into a media center as well. What will I need to do to comp in order to stream media to various computers and TV's? I'm sure I'm missing a few steps or components and whatnot, so any help would be appreciated. Again, I'm retarded when it comes to things like this, so dont assume I know any products or acronyms or anything like that. Help this asian fit the "IT" stereotype!