solonfox

When you click on the "Add or remove user accounts" link, UAC should prompt you for permission to continue. That would be the first thing that you would see.

Is the permission dialog box hiding behind something? It doesn't show up on your taskbar, but your screen should dim and it should be on top, unless you've somehow managed to bring something else around.

Is UAC on or off? Control Panel->Security click on Security Center look to the bottom for "Other security settings," click on the down arrow to show the status of UAC.

Has Windows been activated? Winkey+Pause look to the bottom of the System panel to see the Windows activation status.

-solon fox