I had a list of stuff that I needed to get comma separated and all of the pages I found explaining what to do were wrong.

In the end I had to:

Open Notepad++ (not normal Windows Notepad, you have to download this but it is freeware and very excellent) 

Open or paste your list onto a blank pad

Press [Control]  + H

In the box that appears make sure that you enable the extended expressions like so:

 notepad-expressions.png You have insufficient rights to see the content.

In the Find what: box enter /r/n and in the Replace with: box enter a comma followed by a space and voila, you end up with a comma separated list.