Wylbur,

I loaded a .wav file that was 3 megabytes

How many seconds long was it? A stereo Wave file occupies about 10 MB per
running minute at 44.1 KHz and 16 bits, so a three minute song uses about 30
MB.

A lot of people don't know that you can rename an MP3 file to have a .wav
extension and, amazingly, it will still play in many programs such as
Windows Media Player. So if your original Wave file was a full song in only
3 MB, that's why it was so small.

As for why compressing again made it bigger, that would depend on the
compression settings you used.

--Ethan