I'm going to assume you only want free software, not trialware?
If so, you might use Fair Use software
here, this is completely free (no trials or any of that stuff) but I will warn you that at the end of the install you will be prompted to install some toolbar, just uncheck that box and it will work without the need for that toolbar!
You can also find a few more free programs capable of converting to zune
here. If you look through that page you'll probably find something to like.
- UMPC