How do I rename files with muliple file extensions in the name

I have been unable to find a quick solution to a simply problem concerning the accidental naming of windows files with quadruple file extensions. Windows 10 will allow someone to name a file test.txt.txt.txt.txt but I am also finding programs that double file extensions.In my case I was trying to help somone with 500 files with the extension created twice. My simply solution as example at the command prompt is to type ren *.txt.txt.txt.txt *... then ren *.txt.txt.txt *... then ren *.txt.txt *... OK this seems a little clumsy so where did I go wrong in finding a simply solution from the internet for people that often put a file extension on a file extension that windows would once not like.

The program is Band in the box 2004 . I renamed a group of its files in my docs but these files when copied to another laptop read as xyz.mgu.mgu (mgu being its file extension.

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The fact that I have encountered a situation where something (possibly a rogue script) is doubling file extensions is not my concern but not finding a quick solution is. I have many a time created eample.txt.txt files myself. There are plenty of examples of how to change file name extensions but not how to remove them in groups.

The file type setting in windows is correct. MGU ,SGU ,AND MGI are associated with band in the box.
It recognises its files with or without an extension but windows was associating these files as awindows comshell but was not able to open them. I instructed windows to open these files with B and in the box. Ok but the filkes are stored in my documents and they were named in my documents as song.mgu or song.sgu Then they were put on a USB stick to another laptop where the files became song.mgu.mgu once copied to my documents in that laptop. Ok the guy doesnt want anything changed so let sleepy dogs lie - however what is the simply method of changing a 1000 files that have 2 or more file extensions so that they only have the one file extension and the file name is preserved.

@quickfix2 I made a batch script that may help. Put it in the folder where the duplicated extensions are and run it. I'm putting it as attachment...

Code:

@echo off
setlocal enabledelayedexpansion


For %%a in (*) do (
set name=%%a
call :checkA
call :checkB
)
exit

:checkA
If "!name:~-4,4!"=="!name:~-8,4!" (
set name2=!name:~0,-4!
ren "!name!" "!name2!"
set name=!name2!
goto checkA
)
goto :EOF

:checkB
If "!name:~-5,5!"=="!name:~-10,5!" (
set name2=!name:~0,-5!
ren "!name!" "!name2!"
set name=!name2!
goto checkB
)
goto :EOF