Quicktime and other Apple $%& isn't allowed on my computers so I can't check it myself.
This is, what I found:
Load Windows Media Player and set it as the default MP3 player(put a check mark beside MP3 in File Types, under Tools >Options)
If you find that the MP3 file type is *already* checked, uncheck it, apply, re-check it and apply
Hope that works for you