Creative zen not recognized by computer
I was having the same issues with my Zen Vision M : 30 G.
It was not recogznized on any computer, and when I turned it on after having it off for a large amount of time (24 hours), it would rebuild half way before completely turning on.
I did a TON of research and found nothing but I finally got my Zen to work by trial and error. This is how I did it:
Download the MP3 Recovery tool on the Creative Support Website.
Make sure that the MP3 player is at least half charged.
Turn on the mp3 player, holding the on power switch in the ON position. (Very important to hold the Power switch!)
While holding down the Power switch, reset the Zen by inserting a small object into the hole at the bottom (thumbtack, wire, earring).
A menu will appear: Clean Up, Format (All), Reload OS/Firmware, and Reboot.
I chose Clean Up first and this did not work for me so then I Format. It will remove all of your data on your Zen.
After Formatting, Reboot your Zen and plug it up to your computer.
Run the MP3 recovery tool again.
The Firmware should recognize your Zen, and once installed, so should your computer.
I hope this helps!