NEW YORK - People who use public or workplace computers for e-mail, instant messaging and Web searching have a new privacy risk to worry about: Google's free new tool that indexes a PC's contents for quickly locating data.

If it's installed on computers at libraries and Internet cafes, users could unwittingly allow people who follow them on the PCs, for example, to see sensitive information in e-mails they've exchanged. That could mean revealed passwords, conversations with doctors, or viewed Web pages detailing online purchases.

"It's clearly a very powerful tool for locating information on the computer," said Richard M. Smith, a privacy and security consultant in Cambridge, Mass. "On the flip side of things, it's a perfect spy program."