new hard drive....not recognizing ipod

HELP!!! My hard drive crashed, so I replaced it. I downloaded itunes, plugged in my ipod shuffle...it gives me this message that it is linked to another library and do I want to erase all my music.......How do I get the music I have on my ipod back into itunes? Itunes doesn't even recognize my ipod!!!!

Thank you very much,
ajtaylor77