Congress and federal regulators should avoid imposing restrictions on ways consumers use computers and other devices to listen to digital music and watch movies, the chief executive of the largest U.S. computer-maker said Wednesday. The head of Texas-based Dell Inc., Kevin Rollins, also said entertainment companies should work closely with technology firms to build new businesses delivering music and movies to consumers. Rollins, who took over from Michael Dell as chief executive last summer, was careful to say the company opposes illegal trafficking of digital files.