There are many way to rename miss labeled file with double file extensions.
Below is some ways to fix this problem.
First Thru Windows File properties :
second you rename as follows :
The next is more complicated.
You find the file move /copy the file to another place then do as above .
Another more complicated way is to copy "Files and location " to “C:\filerenamefolder\New Name.one file extension”
remove quote and type command lines in DOS mode. to move/copy the file / files to ned location with only one file extension in the move/copy process. Then manual use del command to remove old file then copy all renamed file back to start location.