There are two ways to format an Mp3 player - one on the computer itself, and one in Windows Media Player. Both methods will end up erasing all the songs on the player, but the player will be "good as new" after that. Sometimes reformatting in this manner will override the player's native formatting and cause problems - this can be reversed in most cases by updating the player's firmware. Firmware upgrades are available from most manufacturers' websites.

WARNING: The following procedures will erase all songs on the player.
Check if the file system is NTFS. If yes, format it to FAT or FAT32. - Connect player to computer, double-click my computer, right click on icon of mp3 player and select format. This only applies to Windows-based computers.
You can also format the player in Windows Media Player itself:
Connect your Mp3 player to the computer and open Windows Media Player. Click on the Sync tab. Pull down the drop down menu underneath the Sync tab by moving your cursor over the Sync tab and left clicking on the little black arrow underneath the Sync tab. Highlight "name of Mp3 player here 1GB" (wording may vary slightly), and then select "Format." - this should erase everything.
-Tha Mp3 Doctor