from http://support.apple.com/kb/HT1911, bold emphasis is mine:
If you cannot remember the passcode, you will need to restore your device using the computer with which you last synced it. This allows you to reset your passcode and resync the data from the device (or restore from a backup). If you restore on a different computer that was never synced with the device, you will be able to unlock the device for use and remove the passcode, but your data will not be present. Refer to Updating and restoring iPhone, iPad and iPod touch software.
also see the following:
Place the iPod in rdecovery mode and then restore via iTunes on any computer. For recovery mode:
Since you do not have a backup on that computer you will have to restore to factory defaults/new iPod.