What’s going on here is that there is a default list of “widgets” that are built into your theme. When you start using the Appearance>>widgets section of your admin, you kick off an if..then statement in your theme which tells the sidebar to ONLY show the things you have added.
More than likely, the items in your sidebar are items that are available as widgets. So, you can just grab the ones you like and add them in as widgets.
Thanks for that answer WPrelief. I was having that problem also.
Can you answer this one as well:
http://wordpress.org/support/topic/twenty-ten-theme-header-image-bug