This is a good question though - how does one create a new .TXT file from scratch? Can it even be done?
Usually what I've done is take an existing .txt file, make a copy, rename the copy, and replace the contents. For .doc files, I open an existing one in Docs To Go, change the content, and then use "save as" which essentially creates a new .doc file. But that's as far as I've ever had to go with these things. Now that I'm thinking about it, it does seem like something I'd want to know how to do. I'm assuming there must be an app for that.
Without a 3rd party application you can not create a txt file on your BlackBerry. I highly recommend BBnotepad for this, it's free and rich in features.