Exergames are a fun and engaging way to participate in physical activity. Exergame users consistently require new content to maintain interest in the activity. One way to provide users with high quality content with minimal development work is to convert existing off-the-shelf digital games into exergames by using the game's "modding" interface. To explore the potential of converted exergames for inspiring high exertion levels we performed a conversion on two popular games: Half-Life 2 and The Elder Scrolls V: Skyrim. The conversions were performed in two stages. The first stage mimics existing conversion techniques and a second stage provides added incentive for players to reach higher exertion levels. A study of 18 participants found that the resulting games support anti-sedentary levels of exertion while falling slightly below national recommendations for cardiovascular exercise. Adding exercise to the games did not affect players' enjoyment.