erm, if you get a good mp3 you shouldn't have any problems with it, if you keep getting poor quality ones with extra background noise added they could possibly be the ones being flooded by netsentry - if you have the latest winmxgroup patch then those would be filtered
many of the search results put there by flooders simply don't download, however some of the netsentry ones do (they either start then don't ever complete, or sometimes complete and are low quality)
if you don't have the patch then it may help to install it and see if you stop getting bad mp3's... <insert comment here claiming not to support copyright breech or some such nonsense for legal reasons>