A software virus that seduced computer users with an e-mail note proclaiming "ILOVEYOU" crippled government and corporate computer networks around the world Thursday and destroyed personal files of music and pictures.

By some estimates, the "love bug" infected tens of millions of computers worldwide, not only spreading by e-mail like last year's Melissa virus, but through instant messaging systems that let people chat on the Internet. In another malicious twist, the new virus was designed to destroy several types of increasingly popular computer files, including those storing pictures, video and music. Computer security experts, stunned by the rapid spread of the virus, urged computer users to delete any e-mail with a subject line reading "ILOVEYOU" and a message saying "kindly check the attached LOVELETTER coming from me." "I stepped away from my desk for 30 minutes and when I came back, there were 177 people who were in love with me," said Ted Canova, news director at WCCO-TV in Minneapolis, who deleted the files and suffered no damage. "That's in addition to the 200 I had when I signed on today." The virus was activated by opening the "LOVELETTER" attachment. That commandeered a computer's Internet browser to visit a Web page, download a program that searches for various types of passwords, and send them to an e-mail account that appears to be based in the Philippines. The Web site was later shut down by its service producer. The FBI quickly opened a criminal investigation, and agents were trying to verify reports that the outbreak may have begun in Asia, possibly the Philippines. Computer security firms scurried to post software on their Web sites to scan for the bug and remove it from infected machines.