i have windows vista and when i open the task manager and click "users" it gives me the option to "log off" anyone else logged onto the computer, when i click the account and then "logoff" i get a message telling saying access denied, but i am the administrator so i should be able to do it. How can i make it possible to do this? Thanks

turn on UAC (ADMIN RIGHTS)
1 start menu
2 click-on your display picture on the top right
3 Turn User Accounts Control on or off
4 check box UAC
Turn in off when done because if malware gets in it will be allowed to make changes to your computer