See other thread re laptop advice. Copy your iTunes folder to the USB HD. Then install iTunes (programme files) on new machine, read up how to de authorise the old computer, and authorise the new one. then copy the iTunes folder into the appropriate place in the new machine. If you have an iPod touch I think you can use it to transfer data.
How to get Windows 10 now: how to download and install Windows 10 even if GWX.exe is missing