Change default category that categories box opens to:

My website is setup in the following structure.

CATEGORIES
------
Products
  Apples
    Red
    Green
  Oranges
    Mandarin
------

Everything is a subcat of the "Products" category.

I would like the category menu to open the "Products" category by default. But I would like the users to be able to navigate to the "Products" category in the breadcrumb trail.

This is the url of my "Products" category
index.php?main_page=index&cPath=1

Admin > Configuration > Layout Settings >
Categories - Always Show on Main Page 1
Main Page - Opens with Category 1

Are you not wanting the "Products" category name to show in the sidebox?
If that is the case, the new version of Categories Dressing can do that; or you can just add to your stylesheet

#categories a.category-top {display: none;}

my main page looked a too cluttered with all the cats displaying, but thanks for the info , it's definitely got the gears turning in my head!