How do I tell it what computer I want the information synced from? All of my addresses in my email got deleted off of my main computer when I synced.

I was trying to sync my bookmarks etc to a new computer. After I synced it, all of my email addresses for my customers got deleted off of my email account on my main computer. They are on my new computer, but need them on my main computer. Can I tell it from what computer to sync the information? Can I undo the sync?

thanks