need some help

Hello, I am a new member hoping to learn more about Windows 7.
My pc is an acer and its 6 months old.
Last week,I was online and our power popped off.
Then it came right back on and then did the same thing 2 more times.
I then turned off my modium by way of the power suge plug in.
Unplugged it at the wall. When I got back online the next day,
as soon as I turned my modem back on my pc turned on without me turning it on.
It had crashed and I gotit back up and my virus protection had crashed too.
My son in law tells me there is some sort of a setting that i can change so the next time the lights go off the pc will not turn back on.
I just looked for this setting and I have no idea what i am looking for.
hope someone can help me,
Thank you
lacjud

Thank you so much Rich!!!!
My son in law was going to do this for me the next time he came over however I was nervous about our power which went off twice last week and stayed off for hours,I really like this forum and will be referring it to all I know online who has windows 7.
lacjud