Living Letters is an adaptive game designed to promote children's combining of how the proper name sounds with their knowledge of how the name looks. A randomized controlled trial (RCT) was used to experimentally test whether priming for attending to the sound-symbol relationship in the proper name can reduce the risk for developing reading problems in the first two grades of primary education. A Web-based computer program with more intensive practice than could be offered by teachers affords activities that prompt young children to pay attention to print as an object of investigation. The study focused on a sub-sample of 110 five-year-old Dutch children from 15 schools seriously delayed in code-related knowledge. Outcomes support the need for early remedial computer programs, and demonstrate that, without a brief but intensive treatment, more children from the at-risk group lack the capacity to benefit from beginning reading instruction in the early grades. With an early intervention in kindergarten, children with code-related skills delays gained about half a standard deviation on standardized tests at the end of grade 2. (Contains 1 figure and 5 tables.)