What is the significance of the National Information Infrastructure Protection Act?

What are the three-tiered approach of the Presidents Working Group on Unlawful Conduct on the Internet?

You have been asked by your manager to look at a particular file on a suspects PC. He wants to do this quickly, while the suspect is at lunch, so there is no time to remove the hard drive. When the suspect leaves for lunch, the PC is left logged on.

If you open a file, what will change?