How will a 'fail' in a course affect chances at graduate school admission? I'm a second year computer science student in Australia. I hope to apply to one of the top 10 US universities for MS or PhD program. I have received high distinction (highest grade possible here) for all my courses since my first year of university, have done an internship at a major company, and have published one paper. However, I received a 'fail' for a course I took at my current university while I was a senior in high school, which shows on my university transcript. Will this greatly affect my chances at graduate school?
Short answer, since I've already addressed a similar case in the answer mentioned above: this should hurt you very little so long as you can maintain your current record throughout your undergraduate program of study. When I consider graduate applications, I am not interested in how a person performed at age 17 or 18; I am interested in how he or she will perform in my program. Four years of high marks and outstanding additional activities are a good indicator. One bad grade from high school is irrelevant. 

If the transcript is sufficiently vague that someone could possibly be confused about this, have one of your letter writers mention the situation in the letter. But my personal feeling is that even this is unnecessary.