If you are trying to perform an action in Vista that requires administrative rights - such as running a program, right click the shortcut for the program and select "run as administrator" and then click OK when UAC prompts you to confirm that you wish to proceed.
Note that you're off topic for this forum, which is dedicated to Windows Live OneCare. You may want to try the Microsoft Public newsgroups here: http://www.microsoft.com/communities/newsgroups/list/en-us/default.aspx for further help with Vista.
-steve
Microsoft MVP Windows Live / Windows Live OneCare Forum Moderator