This is because you didn't set the path of the javac.exe into your environment variables. This can be set as follows:
Go to "System Properties" =>"Adnance" tab => "Environment Variables" command button at the bottom of your screen.
Now from the bottom list box select PATH and click "edit" button to edit.
Now add the path of drivename:/javaFolder/bin separated by semi colon (;) with other paths that are set already in your system.
Be careful while adding these path to PATH as there will be some other paths already shown, those should not be deleted.
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