I don't have a desktop computer anymore because everything I need is on my laptop computer - a MacBook Pro. Although the speakers of the MacBook are actually not bad, I prefer my normal hi-fi system for listing to music and watching movies. Therefore, I have a cinch connector cable to get the sound from the MacBook to the hi-fi system. But that bounds me close to the hi-fi system and the MacBook is not portable around my room anymore.
The solution here is Apple's Airport Express. For this purpose, it acts as a audio streamer. It has audio output interface and connects to any WLAN. Hence, the cinch cable now goes into the Airport Express and I stream the audio from iTunes to it. There is my music on my hi-fi system without any cable going out from the MacBook.
The installation is actually quite easy. It comes with a CD on which you find the tool
that lets you configure how the Airport Express should work. It can establish its own WLAN or connect to an existing one for which you have to provide the access information, of course. It has a couple of more features that I don't use such as acting as a print server if you connect a printer to its USB port.
One problem, however, still remains. iTunes lets you only stream music to the Airport Express. Watching movies or TV is not possible. The solution here is the application
from Rogue Amoeba, available for Mac and Windows. It allows you to stream any sound from any application to Airport Express. This is actually what you expect would work out-of-the-box, but you have to invest $25 for the current single-user licence price. By adding the so-called Extra Instant Hiack it can steal the sound output from any application and send it to Airport Express. This even works for EyeTV and with the included video player also for movies.