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http://www.liveatc.net/archive.phpYou can choose a date, time, and the facility you want to listen to. They are in half-hour increments, though. You can always just pick a busy airport at what is typically a busy time and you'll have plenty of activity. If you have a PC, you can use Windows Movie Maker to shorten the sound file. You can then "publish" the "movie" (it'll just be a sound file with no video) as a .WMV file, so you'll need to utilize Windows Media Player to play the clip.
It's a rough way of doing it, but, it'll work. And since you don't have the sound recording/editing software, then it's about your only option.
Hope this helps!