Removing ^M characters in VI

When porting a text file from Windows to UNIX you will quite often get a ^M on the end of every line. Apart from look bad and make it hard to read, if you text file happens to be a script, then this can also effect the way your script is run.
To remove the ^M characters at the end of all lines in vi, use this command.
To get the ^V you need to type Control+V and Control+M for the ^M. However when you type this, it will appear on the screen like this:

In UNIX, you can escape a control character by preceding it with a Control+V.
The %s command is the VI search command, here’s how it works.
old_string is the the string you want to replace
new_string is the new string you want to replace the old string with
g to make the changes globally through the whole document.
For some more tips on using VI have a look at my 10 Usefull VI tips post