Repeat this procedure for both the english and metric folders where you have no custom classes.
Start the Manufacturing application.
Choose Tools→Convert Tool Library.
In the Convert Tool Database dialog box, navigate to and select your existing tool library from a prior release, and click OK.
For example, to browse for the English file in a default location, you might select …\NX 7..0\MACH\resource\library\tool\english\tool_database.dat.