Nearly all of my clients with
A)  More than one computer or device in the home  that accesses internet or
B)  A laptop that they like to move around their home

use a router connected to their DSL or Cable modem.

A router, routes traffic to all of your internet connected devices.  Some routers do a better job of managing your internet traffic than others.

I have said before that the Apple Airport Extreme is an outstanding router for its ease of use.  However, while it can be used with both Windows and Mac computers — the $179 price point may not be worth it for some people.

So I want to give you an alternative router recommendation.

The LinksysWRT54GL.    This cannot be purchased in stores to my knowledge, but NewEgg currently has it on sale for 56.99 (reg. 79.99).  This model has been around for a while, but it is very customizable.  If you are technically inclined or know someone who can help you — this router can be customized to deliver a very balanced traffic flow to all of your computers and gadgets.  Here is the direct link.
http://www.newegg.com/Product/Product.aspx?Item=N82E16833124190&cm_re=linksys_wrt54gl-_-33-124-190-_-Product

Final note:  routers do use wireless radios inside.  They go bad eventually.  If you have gotten more than 3 years out of your current router, it may be time to consider a replacement.   I have seen them last 1 year and seen some last 6 or 7 years.