After you install and input the commercial release serial number and activate the product you should be using the commercial release. The type of serial number and activation is what determines the student version from a commercial version.
What is happening that you believe you have the student version when you use the software after this install and activation? Does the application title bar indicate the application is a student version? Is the serial number the correct number for the commercial version if you type ABOUT at the command line, then click the Product Information button on the About dialog box?
You can delete the file containing the activation and reactivate the application by deleting the trusted storage file. The file with a name like adskflex_00691b00_tsf.data is in the "C:\Documents and Settings\All Users\Application Data\FLEXnet" or C:\ProgramData\FLEXnet" folders.
You can completely remove all Autodesk software by following the Removing all Autodesk software products from system to ensure a clean install Technical Solution.
Douglas Lauritsen, Autodesk Product Support