OWN is off and running.According to preliminary nationals from Nielsen, the Oprah Winfrey Network drew 1 million viewers during primetime Saturday. Its top show for the weekend was “Season 25: Oprah Behind the Scenes,” with 1.3 million tuning in. Net was the No. 3 ad-supported cabler Saturday night in the women 25-54 demo — clearly the sweet spot for the Winfrey crowd — behind ESPN and USA Network. Sunday’s top show was “Ask Oprah’s All Stars,” which features “Oprah” talkshow regulars Dr. Oz, Dr. Phil and Suze Orman chatting with a live audience. Show drew 602,000 overall viewers. OWN’s primetime shows will launch in their regular timeslots this week. “Oprah Behind the Scenes,” a chronicle of the final season of her syndie yakker, will air at 8 p.m. Fridays.