70s/80s Horror Movie Question

[drhum23]

Trying to locate a haunted house movie from the late 70's/early 80's. A group is trapped inside the house and at one point, a guy tries using a circular saw to cut through the front door, but it doesn't damage the wood. Eventually, while the rest of the group looks on, he starts cutting into his own hand. Any ideas?

For extra credit:

More obscure, not horror-related. Early 80's comedy. There's a scene where some people are about to do some sort of "science experiment" (a couple guys had on lab coats as I remember), and it involved girls getting naked. Synth/80's new wave music was playing and there was a close-up shot of a girl pulling down her underwear. Pretty sure it aired on HBO in the early 80s.

[Rayo Casablanca]

The horror film you're thinking of could be THE EVIL (78) http://www.imdb.com/title/tt0077524/?ref_=fn_al_tt_1

[drhum23]

Rayo - Thanks a million! That's it, indeed. It didn't take much searching before I found an online review with an actual picture of the scene I was describing!
stomptokyo.com/badmoviereport/reviews/E/the_evil.html

Much appreciated!