Here is how to restore the default Windows Vista Sidebar Gadgets.
Q: I inadvertently clicked Uninstall when I was trying to delete the Calendar gadget in the Windows Sidebar and it's completely gone from the gadgets list. How do I reinstate them? I don't prefer third-party alternatives.
A: To restore the default gadgets that are installed with Windows Vista, use these steps:
Note that the above option will be enabled only if one or more of the built-in gadgets had previously been uninstalled.