Emacs 24 with tramp on windows 7 can't find plink

I am running emacs 24 and I want to set up tramp to read/write file on
my ubuntu machine.

When I emacs 24 on windows 7 tryinng to open a remote file by C-x C-f
/[email protected]:/home/mikes , tramp cannot find plink program. And
i did print the exec path, I do have C:/Programs/Putty in my exec
path:

exec-path is a variable defined in `C source code'.
Its value is
("C:/Programs/PuTTy" .....)

But I still get

plink -load 10.136.11.77 -t env 'TERM=dumb' 'PROMPT_COMMAND=' 'PS1=#$
' /bin/sh && exit || exit
plink is not recognized as an internal or external command, operable
program or batch file.

I have this in my .emacs:

(require 'tramp)

(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/") t)


(add-to-list 'exec-path "C:/Programs/PuTTy")
(if (eq system-type 'windows-nt)
    (setq tramp-default-method "plinkx"))

any idea how to fix my problem?