From Help and Support:
If Task Manager has been disabled, you can re-enable it if you have
administrator privileges on the computer.
To enable Task Manager on a computer running Windows Vista Home Basic or Windows
Vista Home Premium
This procedure requires you to edit the registry. An incorrect change to your
computer's registry could render your computer inoperable. We strongly recommend
that you back up the registry before making any changes. For more information,
see Back up the registry.
Click to open Registry Editor.? If you are prompted for an administrator
password or confirmation, type the password or provide confirmation.
Navigate to the following location:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies
Double-click System, double-click DisableTaskMgr, change Value data to 0, and
then click OK.
To enable task Manager on a computer running other editions of Windows Vista
Click the Start button , type gpedit.msc in the search box, and then press
ENTER.
Under User Configuration, double-click Administrative Templates.
Double-click System, and then click Crtl+Alt+Del Options.
Double-click Remove Task Manager, click Disabled, and then click OK.
Note
If the Remove Task Manager properties appear dimmed, your network administrator
has prevented you from changing these settings. Contact your network
administrator to have Task Manager enabled.
