Thread: Unable to switch between the users

I have setup auto logon using Administrator account. I have only two user accounts i.e. Administrator and Guest. When I start my computer, it logs in as a Guest. Also, I am unable to switch between the users. Even I cannot do any administrative work because when I try to do; UAC pops up and Continue button is also grayed out. Can anyone know about this? How to fix this issue? Please help me.

Thanks in advance.

Do the repair of your Windows Vista installation or else do the re-installation of Vista. As you are saying the UAC is turned on, then there is no option except the repair or reinstall.