I don't know how to purchase my tickets online without registering and it won't allow me since there isn't a place for a US address. It's only 2 of us traveling but I want to get this done and I don't know how...is there another way to go around this? I really want to get our longer trip tickets purchased before we leave for our trip in a few weeks. HELP!
If you're booking the night train from Salzburg to Venice, you have to get it from the Austrian site, not the Italian. I know many people have booked tickets through Trenitalia with no problem, especially for straight journeys on fast trains, and others have reported some issues. If it's giving you this much trouble, you could also try a US web site: http://ricksteves.raileurope.com/us/rail/point_to_point/triprequest.htm.
Just use the address of your Italian hotel. The address isn't critical since everything is via email. Second, what are your dates and where are you traveling. Be careful when using the EuropeRail site. ER is a travel agency and not a train company. Often the tickets they sell are limited to specific trains and will be marked up over full price to cover their fees. It is always best to use the national train site when booking tickets.