Thank you. You show me that it works on the standard output port. It help me to pinpoint the problem. I am shy to tell it. I didn't close outport port. Here is the code that works.
(current-directory "C:\Users\Andre\tobedeleted")
(define st-in (open-output-file "out-file.txt"))
(define st-out (open-input-file "in-file.txt" #:mode 'text ))
(define-values (sp out in err)
(subprocess
st-in
st-out
#f
"C:/WINDOWS/System32/WindowsPowerShell/v1.0/powershell.exe"
"dir"))
(printf (port->string st-out))
(printf (port->string err))
(close-input-port st-out)
(close-output-port st-in)
(close-input-port err)
(subprocess-wait sp)