vert urgent: need help with Database

Hi All

i just need to start my project and got frustrated about the Database structure and i need an advice on what is the best structure should i go with.

my project is about ordering system and i start to categorize it like thist:

tble_division
id_div (1,2,3,4,5,6,etc)
name_div (course, non-course, etc)
-----------------------

tble_subdivision
id_sub (1,2,3,4,5,6,etc)
name_sub (Java, Visual Basic, C#,etc)
id_div
-----------------------

tbl_items
id_ite (1,2,3,4,5,6,etc)
name_ite (Book, pdf, CD, etc)
id_sub
-----------------------

tbl_details
id_det (1,2,3,4,5,6,etc)
Code_det (Book123, Book254, CD524, CD856,etc)
price_det
instock_det
-----------------------

so the user(who will place an order) page will look something like this:

Division: please select(drop down menu)
subdivision: please select(drop down menu dependent on Division)
Item: please select(drop down menu dependent on subDivision)
Code: please select(drop down menu dependent on Item)

This structure is working fine with me except one thing.
looking at the Items Table i can see repeated Items like Book, Book, Book, CD, CD, PDF,PDF,PDF) of course every item related to different division and subdivision and has different code but i am sure there is another way to structure this database without repeating the same items. am i right?

so any one can you please help?!?!?

Thanks
Grand