I cannot instal a demo to my XP home PC...
I am getting the error1321: installer has insuficient privilges to modify file mscomctl.ocx..
I am a user with supervisor/administrator type.
Is privilege different from permissions?
And how can I make sure I can install this demo?
Thanks for your help in advance..

That file is a system library (OCX) and these files can sometimes become unregistered due to frequent installation of applications. Try to re-register the file with Windows by doing this:

START--> RUN and type "REGSVR32 MSCOMCTL.OCX"

Let me know if that works.