Problem with dropping a Primary Key and his Index on Oracle 10R1

Hello!
I´ve a Problem with Oracle 10 R1 and need some help. I have installed a Oracle 10 R1 on a Testsystem and imported a Databaseuser (with Tables etc...)

now i want to update the structure of a table and droped the Primary Key and oracle dropped the pk. But he doesnt dropped the INDEX from the Primary Key. He leaves them on the column.

when i create a Primary Key for a table on Oracle 10 R1 and drop the Primary key the index is dropped to.
That he doesn´t drop the INDEX happend only when the primary key is created on a previous Version of Oracle
like Oracle 8 or Oracle 9.

I need to solve the problem, because we have customers with differenz Oracle Versions and all shoudt get the
some SQL Statements to update her Database Structure.

Greetings
A. Peters

--