Steps to follow to completely remove Extender from a workstation.  

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1.  Open the Dynamics.set file which is located in the client directory of your Microsoft Dynamics GP installation.  Typically the path will be something like C:\Program Files (x86)\Microsoft Dynamics\GP20XX   The XX will usually be the version of GP, either GP 2010, 2013, 2015, 2016, or 2018.  

2. In the DYNAMICS.SET file  – Change the first line, make the number at the top one less than it currently shows.  (ex. 38 to 37)

3.  In the middle section of the DYNAMICS.SET file where it lists all the dictionaries, remove the following 2 lines

3107
Extender

4. Remove the following 3 lines from the bottom third of the DYNAMICS.SET file.  Your actual path name may vary from what is shown below, however the 3 lines will always be located next to each other in the DYNAMICS.SET file.  

:C:Program Files (x86)/Microsoft Dynamics/GP20XX/EXTUD.DIC
:C:Program Files (x86)/Microsoft Dynamics/GP20XX/Data/UDFORM.DIC
:C:Program Files (x86)/Microsoft Dynamics/GP20XX/Data/UDREPT.DIC

5. Physically delete the dictionaries EXTUD.DIC, UDFORM.DIC, and UDREPT.DIC in the above path(s) if they exist.  The EXTUD.DIC will exist as that is the main application.  The UDFORM.DIC and UDREPT.DIC probably will not exist.

6.  Relaunch GP on the machine, and Extender will no longer be loaded.