pb on installation - Mailing list pgsql-cygwin

when i tape this command :
$ postmaster -D /usr/share/postgresql/data &
i have got this error why?

FATAL 1 : File /usr/share/postgresql/data/PG_VERSION is missing. This is
not a valid directory

i forward this manual to install cygwin
http://www.ejip.net/faq/postgresql_win_setup_faq.jsp
and this
http://www.ejip.net/faq/postgresql-7.1.3.README

can you help please
thanls