so high-level it's funny
windows vista security hole: a sound being played on your computer (ie, from a web page) can make your computer do things (ie, delete your documents folder and empty the trash) if your speakers and microphone are on and you have speech recognition enabled.
Microsoft confirms Vista Speech Recognition remote execution flaw. this can be dealt with by requiring a verbal password before accepting commands (mac os x does it that way, afaik). via simon willison.