Play music throughout my house

[carrot]

I've been googling for the past little while, but I can't find anything close to what I want.

I want to be able to sit at one computer on my network and play a song, then have that song play in sync on all the other computers' speakers in my house.
I just received an airport express adapter and I was playing around with the remote speakers feature. That's where I got this idea. I don't care if I can include the AirPort speakers or not.

Anyone know of anything that can do this?

Thanks!

[Paul Komski]

Possibly http://www.kintronics.com/IPpa/IP%20PA%20Systems.html

... but if your house is big enough then it aint gonna sync no more.

[carrot]

That looks somewhat like what I'm looking for...
Although, I don't want to have to use any additional hardware.
Thanks though!