Here's a nice little tip that I found on this site which allows you to merge text files together that you have in a folder.
A. Begin my right clicking in a blank space in the folder with the text files (see Fig. 1) and selecting 'Open Command window here'. See Fig. 2.
B. At the command prompt enter:
for %f in (*.txt) do type "%f" >> output.rtf
See Fig. 3.
[Don't make the output file in the same .txt format or this command will copy each processed file multiple times.]
C. Press enter and the command will run. See Fig. 4.
D. A new file will be generated with the combined content of the original text files. See Fig. 5