Each time a version of BlackBerry Native SDK is installed it creates a SDK Platform configuration file that is read by all versions of BlackBerry Native SDK you have installed. This allows you to build projects for different targets in the same workspace. You can view and select these settings within your workspace options, or on a project level by right clicking on the project, choosing Properties and then QNX. Here is a screenshot of the configuration screen.
You may wish to remove specific SDKs as an option after a BlackBerry Native SDK has been un-installed or if you no longer wish to build for a given target. This is done by deleting the coorisponding Platform SDK configuration file. These files are located in %QNX_CONFIGURATION% directory, which is defined in the bbndk-env batch file located in the BlackBerry Native SDK installation directory. On a Windows® 7 computer this resolves to %HOMEPATH%\AppData\Local\Research In Motion\BlackBerry Native SDK\qconfig.
The configuration files are XML files that can be viewed in any text editor. Open the files and refer to the name entry to find the one you wish to delete. The name entry is the value that is shown in the dropdown in the screenshot above. Here is an example configuration file.