1) Call up the text file in a text editor (Notepad, Wordpad, WordPerfect, Microsoft Word, etc.) and manually delete the lines that you don't want, then re-save the file when done.
2) Use the /write command with the -d switch to delete the duplicate lines.
See /help /write
Personally, I would recommend the first option, as you will be able to see each change as it is done, then save the file only once, rather than having the file be re-saved with the deleted line each time.
