I pondered about this last year myself.
Sorry to "bump", but some may google "How to mute IE" hehe.
Well, I do have half an answer.
Vista only. (or read below)"volume mixer" lets you global mute any running program.
http://news.softpedia.com/news/The-W...er-41882.shtml
"Comment #3 by nimd4 on 2007-11-02, 16:57 GMT reply to this comment
There is IndieVolume which works on Windows XP; Here on Softpedia @ http://www.softpedia.com/get/Desktop-Enhancements/Other-Desktop-Enhancements/IndieVolume.shtml"