please see our rather long thread on default application / creator codes here:

http://www.gnutellaforums.com/showth...?threadid=6616

I was having a huge problem with my files "becoming" iTunes files or QuickTime files on completing a download. It seems to be pretty much resolved though, hope it will help you out too.
PS- I don't use iTunes either, I still love my Greyamp and occassionally use SoundJam.