How Do I Unlock My iPod Touch if I Forgot the Passcode, and I'm Using a Different iTunes?

The Apple iPod Touch has a security feature that allows the owner to require the entry of a four-digit passcode each time the device is accessed. If you forget the passcode, you can unlock the iPod Touch by connecting it to the computer you use to sync it. If you do not have access to your primary computer, you can still unlock it by connecting to iTunes on a different computer and performing a restore procedure, but the restore erases all the device's data and returns the device to its original factory condition.

...
Remove an iPod Touch's passcode using iTune's restore feature.

Step

Plug the iPod Touch into the Mac or PC computer using the iPod USB cable.

Step

Launch the iTunes application.

Step

Highlight the name of the iPod Touch from the "Devices" list on the left side of the main iTunes window.

Step

Go to the "Summary" tab at the top of the iPod configuration information.

Step

Press the "Restore" button and then click "Restore" in the dialog box to confirm your decision to unlock the iPod Touch and erase all its data.

Step

Press "OK" when the restore process has finished and then wait for the iPod Touch to restart. When the device restarts, it is unlocked. You can sync it with any computer or restore your data from a previous backup.