Most of the audio files on Gnutella are mp3 and they are prefered by most. There are a few wma files but these are generally best avoided.
Some files are fakes and even if they show a few MB size they are just kind of dummies designed to block up the network. If you hover over the file name in the search window (with extended tooltips enabled in options) You should see title album artist etc. If you do not it is possible that the file is a fake ...although this is by no means always the case!!!
The fake files tend to come from T3 sourses ..but again not always by any means. It does not really matter which sourse you download from. Many are misslabled on purpose for various reasons, but it is a good idea to go for files with less than about 15-20 hosts. The fakes tend to come in batches of 40 .-50 or more.
I hope this helps a bit
