One more question! There seem to be a lot of very technical people here, so I'm hoping someone can help me. I recently uploaded some audio files that I recorded from a digital piano, using a Zoom H2 'Handy Recorder'. That all worked fine, but since then the sound on my laptop has started sort of echoing, whether it's playing something on youtube, playing a CD, clicking on a webpage - anything, really. It's really annoying, and makes anything on youtube hard to understand.

I assume some sort of setting somewhere has automatically changed, but I can't see what or where it could be. I'm almost 100% sure it only started doing this after I plugged in the Zoom thingy.

Any ideas, anyone? Thank you!

It's ok - I've solved it. It had reset itself, to replicate the sound I could achieve by using my laptop in a cave or a sewer pipe. Obviously.