How to delete a file in Windows with a too long filename?

Solution 1)
From a command prompt:

dir /X

This will list your files or folders in short name format. Then use the short name exactly as written to delete the file:

del LONGFI~1.txt

you are done!  :)
 
Solution 2)
Try this in a Command Prompt.
rd /s first_part_of_subdirectory_name

e.g. if the file is called "C:\temp\Files\verylongfilenames.ext"
rd /s C:\temp\Files