House Haunted by Witch Burned at the Stake

by Anonymous

What is the title of a movie from the late-70's or early-80's where a couple buys a house that is haunted by a witch burned at the stake?

The witch's sister lives by the lake on the same land, and eventually helps the people break the curse her sister put on them.

In one scene, a saw blade flies off of the saw and decapitates someone.

If anyone knows the name of this movie, please help.