CSI: Original Game Cheat
In the first computer game, 2003's "CSI: Crime Scene Investigation," you can easily edit a file in the CSI directory to automatically give yourself the Master rank bonus. Navigate to wherever you installed the game to and click on the SavedGame or Games folder in the main CSI directory. Open a saved game in Notepad (or TextEdit on a Mac), and scroll to the bottom until you see each mission results.
Change the value next to evidence to "100," hints to "0," ranking to "3," bonus to "10," and score to "100." Finally, change the "final bonus" to "25." Save the file, then load that saved game. Your scores should be maxed out and you'll have achieved Master rank.
CSI: Hard Evidence Cheat
In 2007's "CSI: Hard Evidence," a quick cheat at the beginning of the game will automatically unlock all five available cases: "Burning for You," Double Down," "Shock Rock," "In Your Eyes" and "The Peacemaker." When asked for your Investigator Name, simply type "CONFESSION" (all caps, without quotes). All cases will be unlocked.
Using Walkthroughs
Extensive walkthroughs have been written by fans of all five CSI computer games that are freely available online. Generally, these walkthroughs provide the solution for solving all the cases in the best way possible, while getting the most bonus points and all possible rewards. If you're stuck on a level or want the quick solution to maxing out your score, consult a walkthrough. Many can be found at GameFAQs.com.