Windows built-in command compact allows one to compress or un-compress files on a NTFS file system. Using this command we can set compression attributes on a directory also so that the new files added to the directory will be compressed automatically.

To compress all the files in the current directory and also the sub directories and the files within them recursively

compact /c /s *

To un-compress all the files in the current directory and also in its sub directories:

compact /u /s *