I had the same problem, too. In my case it was my fault, because i always looked for an *.iso Data in the downloaded files, afer unpckng the download.
Thanks to the board here i found out who to do it :
Just download Mint an do not unpack it. Under XP you just have to rightclick on the archive. Then choose " Open with". Choose a burningprogramm.
With nero 6 it automatically it opened with the Isoburning dialog.
After burning was finished, i had a bootable CD.