Java 7 seems a behaviour with UAC like older Java versions.
The current Java 6 behaviour seems more correct.
It throws an IOException if we write to c:\program files.
Java 7 creates a file in VirtualStore.

The same problem exists with the system preferences.
With Java 6 we can read the preferences that a system account can see.
With Java 7 we receive a mirror in the user scope. This is a regression.

Here isa test function which behaviour is different in Java 1.6.0_21 and 1.7.0_b100 if UAC is enabled.
 

    private static boolean isWindowsUacEnabled() {
        try {
            boolean isWindows = System.getProperty( "os.name" ).indexOf( "Windows" ) >= 0;
            if( !isWindows ) {
                // Nur für Windows Testen
                return false;
            }
            String osversion = System.getProperty( "os.version" );
            int spaceposition = osversion.indexOf( " " );
            if( spaceposition > 0 ) {
                osversion = osversion.substring( 0, spaceposition );
            }

            double version = Double.parseDouble( osversion );
            boolean isVista = isWindows & version >= 6;

            if( !isVista ) {
                // Nur Betriebssysteme ab Vista und höher, solle auch Windows 2008 betreffen
                return false;
            }

            String userHome = System.getProperty( "user.home" );
            File virtualStore = new File( userHome + "/AppData/Local/VirtualStore/Program Files" );
            if( !virtualStore.exists() ) {
                return false;
            }

            //"Program Files" wird seit Vista nicht mehr übersetzt, nur der Displaywert wird geändert
            //Unklar ist nur das Laufwerk

            String programFilesLocation = null;
            programFilesLocation = System.getenv( "ProgramFiles" );
            if (programFilesLocation == null) {
                return false;
            }

            File programFiles = new File( programFilesLocation );
            if( !programFiles.exists() ) {
                String javaHome = System.getProperty( "java.home" );
                int idx = javaHome.indexOf( '\\', 3 );
                if( idx > 0 ) {
                    programFiles = new File( javaHome.substring( 0, idx ) );
                }
            }

            if( !programFiles.exists() ) {
                // Program Files wurde nicht gefunden
                return false;
            }

            File tempFile;
            tempFile = File.createTempFile( "uac", null, programFiles );
            tempFile.deleteOnExit();

            File virtualFile = new File( virtualStore, tempFile.getName() );
            // Die eigentliche Prüfung
            boolean isUac = virtualFile.exists();
            tempFile.delete();
            return isUac;
        } catch( IOException e ) {
            // ignore weil wir nichts zum Loggen haben
        }
        return false;
    }