First, you don't put songs from and ipod to a computer unless they are purchases. Even then the idea is you synchronize the content of the ipod to the content on the computer, not the other way around.
Options for when an iOS device gets locked because of forgotten password:
Restore (and reset password) on your device by connecting it to the last computer to which it was connected:
iTunes: Backing up, updating, and restoring iOS software - http://support.apple.com/kb/HT1414
If you cannot connect it to the computer to which the device was last connected you will have to use recovery mode to completely reset the device, losing all data:
iOS: Unable to update or restore - http://support.apple.com/kb/HT1808 - recovery mode (e.g., cannot connect to computer last used to sync device, iTunes still asks for a password)