The "Trusted Installer" is the actual owner of the delegwiz.inf file. You need to take ownership first, then change file permissions. Copy/Paste the reg code in the code box into a notepad; save it with .reg file extension. It adds the "Take Ownership" to your right-click context menu.
Locate file, RIGHT-click, select "Take Ownership"
As for the cmd prompt - run it at an elevated administrative level - try bringing up cmd this way -
START | type cmd.exe | RIGHT-click on cmd.exe | select "run as administrator"
You may be interested in activating the Vista hidden admin account - no UAC for it; it has the admin token for elevation. Using same ELEVATED cmd screen -
net user administrator /active:yes