Minimal requirements-networking lap and desk

I will soon take the plunge and get a laptop. What I want to do is not have to physically connect it to my cable internet, but want to set it up so that I can turn on/log on with my desktop and use the laptop in another room.
Don't know if I really need a wireless router, and am not quite sure if my current custom desktop is set up for WiFi.
Does anyone here do this same thing, and if so, what hardware/peripherals do you use?

 

You will need a wireless router. I use the Linksys WRT54GL. Works well and can be flashed to a better IOS if you need it in the future.

E