If Vista will not download and play mp3 files.

1. Go to Control Panel, double-click "Default programs"
2. Click "Associate a file type or protocol with a program" - takes a few seconds to load the list.
3. Double-click the file-type under the "name" column (such as ".mp3"). It is probably showing something already, like "Windows Media Player", but don't believe it.
4. Now you'll have a list of "Recommended Programs". Double click the one you want. I chose "Windows Media Player" even though it was already "supposedly" set to that. Again, it will show "loading" at the bottom of the screen for a few seconds.

It should now work, try again.