Hmmm I have not really figured out why it can not see my mapped drive when it is not a service. However if you have same problem as me, here is a workaround:
Make a bat file like mount.bat, place it in C:\temp\ and put the following code into it:
set SHARESERVER=servername
set SHARENAME1=sharename
set SHAREUSER=username
set SHAREPASSWD=password
echo %date% %time% : "%cd%\mount.bat" >> C:\temp\mount.log 2>&1 2>&1
net use * /delete /y >> C:\temp\mount.log 2>&1 2>&1
net use s: /delete >> C:\temp\mount.log 2>&1 2>&1
net use s: \\%SHARESERVER%\%SHARENAME% /user:%SHARESERVER%\%SHAREUSER% /persistent:yes %SHAREPASSWD% >> C:\temp\mount.log 2>&1 2>&1
Create a scheduled task, which execute the bat file at "any user logon". And very importent; Change the user/group to SYSTEM.
This will the mounted network drive visable from BeoPort/Player