movemail doesn't recognize path correctly on windows

[najja]

I use fetchmail (cygwin) + gnus to read my email, however, gnus
refuses to convert mbox generated by fetchmail to nnml. My .gnus looks
like this:
-----------------------------------------------------------------------
(setq
 user-full-name "najja"
 user-mail-address "sumnerbarney@gmail.com"
 display-time-mail-file "c:/var/spool/mail/Administrator"
 message-default-charset `utf-8
 nnml-directory "c:/GnusMail/"
mail-sources '((file :path "c:/var/spool/mail/Administrator"))
 gnus-select-method '(nnml ""))

-----------------------------------------------------------------------

So none of the path deals with drive other than c:, but when I run
gnus by "M-x gnus", it shows a cryptic error:

Movemail: Permission denied for d://(1 return). Continue? Yes or No.

No matter what I choose, it won't convert c:/var/spool/mail/
Administrator to c:/GnusMail.

My HOME enviroment variable is pointed to D:. After I changed it to
C: , gnus successfully converted c:/var/spool/mail/Administrator to c:/
var/spool/mail/Administrator but nothing shows up in the {nnml}
server.

Anyone here use fetchmail + gnus scheme? How do you make it work?