To use it with Windows, the iPod's storage will need to be reformatted (to a Windows format), so it will be erased. Although a Mac can read the Windows format, a Windows PC cannot read the Mac format (without extra-cost third-party software). So, Windows cannot access the data currently on the iPod, using iTunes or any other application.
Do you have access to that previous Mac? If you do, you should transfer the song files directy between that Mac and your Windows laptop. You can use an external drive that is formatted using "FAT," which is accessible from both Windows and Mac.
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