If you have formatted the iPod then you are unable to retrieve the music.
iPods will only let you work with one computer IE:
If you set it up and download songs on one computer, then take it to another computer, the iPod will want to reformat so the songs are cleared from the iPod and cannot be transported to another system.
This is to prevent illegal copying etc.
You could use a tool such as Senuti, but it is only available for the Mac platform, and from what you say you have a windows system?
Senuti will get all the songs off your ipod and allow you to save them to your hard drive (for later conversion) providing the songs are still there. However, a similar program for Windows is available here:
http://www.ephpod.com/
I have never tried it so don't know if it works, so you will have to read through the help file. I hope this is of some use.
Regards,
Kyomii