There are multiple softs on the internet that allow you to merge files. However, ther is an easily forgotten alternative to all this softs : the "copy" command-line option
Then, move to the folder in which the files are stored by typing "cd [foldername]". Finally, type "copy [source file 1] +[source file 2] +[srcfile3] +[...] [destination file]". copy will merge every source files into the destination file.
Note that this tool can be used in binary mode ("/B" option) to merge non-text files.