As of March 31 the Chemical Abstracts Service will not support older versions of SciFinder Scholar. If you are not using SciFinder Scholar 2006, please go to this link and follow the links for the "SciFinder Scholar Download Page."
You do not have to uninstall older versions of SciFinder Scholar, but if you do, then make sure you download the site preference file to the folder that contains SciFinder Scholar.
There are a few new features in the 2006 version:
1) Easier to look up specific references from journal name, author, title, year, and more
2) New structure and reaction search tools: repeating group, variable attachment
3) Structure similarity searching
4) Search sb-structures in structures and reactions are highlighted.