But the company's plans for pop-up ads and restrictions on copying have sparked worries that the service may be eroding consumer control in favor of Hollywood and advertiser interests.

Is it becoming TiVo - their way?

''Consumers are very distrustful of technologies that seize yet another opportunity to offer up advertising,'' said Mike Godwin, legal director of Public Knowledge, a public interest group. Whether the fears are founded or not, he said, ''it feels like TiVo is taking away some of the prerogatives and flexibility that TiVo TV watchers have become accustomed to.''

TiVo officials say that starting in March users will begin to see static images, such as a company logo, appear on their television screens as they fast-forward through commercials. The billboard-like ads - which will last about four seconds for a fast-forwarded 30-second spot - may offer giveaways or links to other ads.

A pop-up recording ''tag'' also is planned: a ''thumbs-up'' icon would appear during TV show promotions and allow users to instantly place those programs in their recording queue.

TiVo officials contend that the new features will not be any more intrusive than the ''thumbs-up'' icons that already appear during some commercials and shows. But to some customers, the impending advertising changes smack of betrayal from the innovators whose hard drive-based gizmo lets TV viewers record programs, fast-forward through ads and pause at will.

Some skeptics worry that TiVo's planned use of Macrovision Corp.'s new copy-protection scheme signals more boundaries on what shows they can or cannot record - even as TiVo prepares to unveil a new service later this year, called TiVoToGo, that will let users record shows onto DVDs or transfer them to computers.

Macrovision has developed a feature that will allow content providers - the people who produce television shows - to place restrictions on how long a digital video recorder such as TiVo can save certain kinds of programming.

TiVo officials say the new restrictions will apply only to pay-per-view and video-on-demand programs.

Industry watchers say TiVo has no choice but to make peace with networks, cable and advertisers.

''TiVo has to become more advertising-friendly because, at the end of the day, TV runs on advertising dollars and companies that are part of that food chain have to acknowledge that,'' said Tim Maleeny, director of strategy at Publicis & Hal Riney, a San Francisco-based advertising firm.