If you are getting an error in your sidebar that "Windows Sidebar Is Managed By Your System Administrator" and you *are* the system administrator, here's a regedit fix you can try to fix the problem.

For the regedit program, find the HKEY_LOCAL_MACHINE + SOFTWARE + Microsoft + Windows + CurrentVersion + Policies + Windows + Sidebar section. Looking in the right pane, if there is a value called TurnOffSidebar delete it.

Then go to the HKEY_CURRENT_USER + SOFTWARE + Microsoft + Windows + CurrentVersion + Policies + Windows + Sidebar section (same path, just a different starting point, user instead of machine) and again look for a TurnOffSidebar on the right. If it's there, delete it.

If there was a value in either case, you should be able to restart the sidebar (or reboot) and this will take care of the "Windows Sidebar Is Managed By Your System Administrator" error.