VNC Server off when I log off

[F. L.]

Hi everyone,
I'm using VNC 4.1.2 free edition on windows xp Pro Ver 2002 SP2

I registered VNC Service

I have 2 windows account (admin & user). When Windows starts,I login as 
admin and VNC Service is up & running. I can use VNC viewer from another 
computer.
But when I log off admin and swicth to user, VNC Service is off and I'm no 
longer able to view from another computer.

How to set up so that VNC Service will keep up & run eventhough I log off 
and switch user

Thanks a lot for your help.