Connecting two home computers through router

Hello,

My desktop and my brothers laptop are both connected wireless to the internet through the same router.

Is it possible to connect my pc to my brothers locally (so without uploading & downloading from the internet, just sending over local network through the router to eachother?)

Some things I'm thinking of:
- Sending a file from my brothers pc to my pc, so I can print it
- Streaming a song/playlist to my brothers pc so he can listen to it
- Letting me explorer files on my brothers laptop that are mine (and vice versa)

If this is possible, and you could explain it to me, then I would love you forever!

Thanks in advance!

Some more details:
My desktop is running Windows XP Home
My brothers laptop is running Windows XP Pro
My router model is Philips CPWBS154/18