Postmaster won't run as service on Cygwin

Hi,

I installed an postmaster for trainig and developement on my home box.
It should run as win 2000 service on cygwin.

Cygwin sits in   I:\cygwin
Data is   I:\db_data\psql_data
Data folder belongs to the user    postgres.benutzer

I (postgres) can start the postmaster on a command line.
I can log in and everything seems to be OK.

Then I wanted to start it as service and ran as administrator on a
cygwin console:
cygrunsrv --install postmaster --path /usr/bin/postmaster --args "-D
/cygdrive/i/db_data/pgsql_data -i" --dep ipc-daemon2 --termsig INT
--user postgres --shutdown

postmaster shows up in the service-management-console
When I try to mouse-click it, it shows 2 boxes on the progress bar, then
stalls and after quite a while it throws  Error 1067   Process got
unexpectedly stopped
"net start postmaster" run as administrative user throws the same.
"net start postmaster" run as uster postgres gives System-Error 5
access denied


What now ?

Andreas