catherinehale

 

Do you have the sidebar icon in the notification area? If so right click it
and left click properties and make sure you have a checkmark in the box
"Start sidebar when Windows starts."

 

OR
Start/Run  and type in
sidebar
OK

See if it keeps working after that

 

OR
You should have a spare copy of sidebar.exe in the Windows\winsxs folder. You'll need to search for Sidebar.exe to find it, as the folder names use GUIDs.
Type sidebar.exe into the “Search” at the top

Then copy it into Program Files\Windows Sidebar and see if that fixes things.