gVim control characters on Windows

from :help CTRL-V-alternative:

                                                *CTRL-V-alternative* *CTRL-Q*
Since CTRL-V is used to paste, you can't use it to start a blockwise Visual
selection.  You can use CTRL-Q instead.  You can also use CTRL-Q in Insert
mode and Command-line mode to get the old meaning of CTRL-V.  But CTRL-Q
doesn't work for terminals when it's used for control flow.

Another Way, specific for ^M, would be to use :%s/\r//g since ^M is a carriage return.