How can I watch the exorcist?

I have watched the 2nd and 3rd movies of the exorcist by Alphred Hitchcock. I tried to watch the first one in the series but everytime the girl starts talking in that horrible voice when she is possessed I turn the DVD off straight away. Please tell me how I can watch it right through till the end and how can I watch it when hearing that scary voice? I have had nightmares ever since I seen it but cant get over the movie. Everyone else that has seen it tells me the story but I tell them not to tell me about it because I havent seen it right through yet. Please help me I know I should watch it but I am very sensitive and get frightened alot. Sorry.I want to watch it. Should I turn the volumn off when that voice comes on and just read the subtitles instead of getting scared?