I found that under C drive like C:\Program Files and C:\Windows, the Power User don't have access right on it and the User group only have Read & execute right. If I want to copy files under this two folders, is it necessary take the Ownership of TrustedInstaller and change to local administrator. And then change the access right for Power Users accordingly?

Hi, with Windows 7 the Power Users group is obsolete and has no longer the rights, it had in Windows XP. Program Files and Windows are both system protected folders, so it is not intended to manually write stuff into these locations - especially not by limited users. Now it depends from the application, which kind of workaround can be found, since some workarounds are really opening the security gaps again, which have been closed with Windows 7. Maybe get the programmer at your hands and tell him the requirements, i.e. users should never have to write into subfolders of Program Files or into Windows folder. You could try to install the application to a folder outside of Program Files (optional Program Data) and adjust permissions for Users. Best greetings from Germany Olaf

But if I really want to copy files to C:\Windows and C:\Program Files, is it necessary to take the Ownershop of TrustedInstaller first and chanage to local administrator before I can assign the access right to Power Users.