ITunes Library wants to erase my iPod if I sync, what can I do? Thanks

I installed iTunes on my new PC, I want to sync with my iPod Classic, It says I am synced with another iTunes library, but I dont remember my old iTunes ID or PW, it's been a long time. I tried to retreve it by entering old email addresses, but that didnt work.

What do I do? I dont want to erase and loos all the stuff on my iPod and if I sync, is appears that is what will happen.