Found on another forum, thry this
Re: Sidebar full of calendars and takes a long time to start up
To reset Windows Sidebar to the defaults, try this. Exit Windows Sidebar
and navigate to C:\Users\(Your Name)\AppData\Local\Microsoft\Windows Sidebar
(the path is hidden). Rename the file Settings.ini to Settings.ini.old.
Restart Windows Sidebar. A new Settings.ini will be created.