Any ideas on how to find my long lost sister?

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My sister is 22 years old and I have never met her. I have one picture of her from when she was about 6 years old, but that's it. Last I heard she was living in Richmond, VA. I knew her mother's full name until she got married, now I haven't a clue. I don't know if her stepdad adopted her and changed her last name or not (she had my dad's last name). I have tried everything affordable to find her. I have searched online, I have searched on MySpace, I've even contacted Oprah. The only two people who could provide any information are deceased (my dad and grandmother). I wish I had started this search earlier when they were still alive, but you know how you always think you have more time? Besides, I was young and the world revolved around me (you know how that is, lol). If anyone can provide any websites or information to help, I'd appreciate it. I really can't afford a PI, that's why I haven't gone that route. Thanks in advance.