This might explain why the old mic doesn't work with the newer Macs:
http://docs.info.apple.com/article.html?artnum=18275I'd suggest a USB microphone/headset. My kids both have headsets they use for WoW and Skype.
Something like this:
http://www.newegg.com/Product/Product.aspx...N82E16826275009Just make sure it works with Macs - not all do.
Here's another - more expensive, but highly rated:
http://www.amazon.com/apple-Only-Audio-85-...135&sr=1-16NOTE: don't buy the cheapest one you find - in our experience, the $20 and under ones tend to break easily - my younger son has duct-taped his microphone arm on!! (wires still ok - but the plastic gave way)