I need to login to a machine that I am an administrator on, but the machine is currently locked and there is no option to switch user. The little arrow to 'Switch user' is missing and Ctrl Alt Del doesn't present the option to switch user. I know how to fix this in the registry if I can get logged in, but I can't login because there's no option to switch user.

Is there a keystroke combo that allows you to provide alternate credentials?

Thanks - Tom