Windows system call without Command Prompt window?

 From Lispworks in XP, I'd like to use plink to set up an SSH tunnel. Is 
there a way to avoid having the Command Prompt pop up when I do this? I 
have tried the following two:

(sys:call-system-showing-output '("plink.exe" "-load" "saved" "-batch") 
:wait nil :output-stream nil)

and

(sys:call-system '("plink.exe" "-load" "saved" "-batch") :wait nil)

Mitch