Thanks for the response FE, but I obviously didn't explain the problem very well. Normally (and indeed currently) when I use MSN Messenger I speak into the mic and all I hear is my friend talking from her side, and the same for her. A while ago I had it so that I heard my own voice, quite loudly, coming back through my speakers. I somehow fixed without noticing, now my friend had the same problem. However, she just fixed it while I was writing this, by going into Volume Control and decreasing the level of the microphone. Sorted.
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