|Here is a quick howto on changing the default audio device in windows XP|
1. Go to control panel (Start > Control Panel)
2. Go to "Sounds, Speech, and Audio Devices", and then click on "Sounds and Audio Devices". If in classic view, just click on "Sounds and Audio Devices".
3. Go to the "Audio" tab
4. Here you will be able to select the default device for recording/output. To Send the sound to your TV, select from the list that best describes it (HDMI Audio).
5. Click "OK", you should be able to get sound from your TV now :D
Hope this helps with the TV/HDMI audio issue anyhow, I am not sure how to go about connecting "other" speakers to the system unless they use the standard "Headphone/Speaker" connector