My iPod has fallen out with iTunes. What's the safest way to get them back on speaking terms? My girlfriend moved her iTunes library into Dropbox and now her iPod Touch doesn't recognise it. I moved it back to where it had been before, but this wasn't enough to get it to sync without threatening to erase everything.

I'm planning on using iTunes to back up the iPod, copying the back-up file to somewhere safe, then syncing. I hope that I can then restore any lost notes etc.

Firstly, will this work? Secondly, I think that the music she's bought recently through the device won't be backed up. How can I retrieve that?

The OS is Windows XP.
Yes, it should work.
All music she has bought is under Purchased in Quick Links menu in iTunes Store in latest iTunes. It can be redownloaded from there.