How to sync moved iTunes library onto iPod?

I bought a new laptop and downloaded iTunes. My old desktop had all of my 800+ songs on it, so I copied all of my songs on to a 8GB memory stick deal and put all the songs on to my new laptop's iTunes library. I told it to sync and it asked me if I wanted to transfer, I said yes. Then it told me a ton of my songs could not be synced because they couldn't be found. Then my computer was suddenly unauthorized to have some other stuff on it. All of my songs have a "!" on it as well. My iPod is now song-less and I NEED HELP!