I have a Windows 7 (32 bit, service pack 1) on my laptop and, whenever I launch my sound editor (Ableton Live 8), all other programs (Firefox, Chrome, Skype etc) stop outputting any sounds. Even when I try switching the order of steps (opening Ableton first and then launching a browser, for example) it doesn't work.
In Control Panel > Sound, I have the laptop speakers as the default output and, as soon as I close Ableton, all other programs are able to make noise again.