Restoring (or reformatting) your player's software to its original factory settings is a last resort for fixing a problem with your player before you send it to Microsoft for service.
How to reinstall your player's software
Start by trying to reinstall the Zune player software without erasing it.
Set the Hold switch to the unlocked position.
Press and hold the top of the Zune Pad and the Back button at the same time, and keep them down until the Zune player restarts.
What if my player doesn't respond?

After you release the buttons, press and hold the following combination of buttons, depending on your player model.

If you have the 30GB Zune: Press and hold the Back button while you press both the left side of the Zune Pad and the center of the Zune Pad.

Continue to hold these buttons until your player restarts and the message "Clearing contents. Please wait" appears on your player's screen, followed by CONNECT ZUNE TO YOUR PC.
Connect your player to the computer that has the Zune Music + Video software installed, and then update it. It should take about 30 minutes to update the player software.
What if the Zune software doesn't detect my player?
Resync your content to your player.
If your player still doesn't work after you reinstall the player software, you'll need to send it in for service. Please visit http://service.zune.net to get help.