Soon even personal computers won't be safe from the hard sell. Marketers from Silicon Valley to Madison Avenue are now saying that, if commercials can appear on television programs, they can appear on your computer programs, too.

"It's a thought that's been in our minds," said Fred Gibbons, president of Software Publishing Corp. in Mountain View, Calif., considered one of the most innovative marketers of personal computer software.

With sales of personal computers soaring into the millions, the idea of using them as electronic billboards becomes increasingly attractive because of the demographics of owners and the machines' graphics capabilities.

"I think personal computer displays are still text-oriented, and text-oriented ads aren't very sexy," Gibbons said. But he believes that, with improved computer animation abilities, personal computer advertising displays could rival television spots in style and pizzaz.

For example, a personal computer owner signing on to a new program might first see a screen displaying a full-color advertisement for a personal computer magazine along with a toll-free number to call for a discount subscription. Or the program might run snippets of other computer software the company sells. What's more, ads could be tailored to the kind of software the consumer had purchased: a financial worksheet program might include an ad from a business magazine.

To minimize the nuisance factor, the messages could be programmed to erase themselves after a specified number of sign-ons.

"I think it's a spectacular idea," said Jerry Della Femina, chairman of Della Femina, Travisano and Partners, the Madison Avenue advertising agency.

Della Femina believes that, as home computers become more of a mass-market item, mass-market advertisers may begin to exploit the computer's potential. "Imagine Procter & Gamble producing a 'Clean the House' videogame," he said.

Major videogame manufacturers such as Activision and Imagic have not explored the idea of designing advertiser-sponsored games but, according to several games designers, it would certainly be possible for a company such as McDonald's to have a Ronald McDonald computer game if it so desired. "And because it would be advertiser-supported, it should sell cheaper," Della Famina said.

Computer advertisements also might appear on the many computer networks that have surfaced in recent years. "You will be seeing us doing something in this area," said William L. Dunn, president of the Information Services Group at Dow Jones, the company that publishes the Wall Street Journal.

With more than 100,000 personal computer and computer terminal users as subscribers, Dow Jones has one of the largest computer networks in the country. Dunn is thinking of having commercial messages sent to people's screens as they link up to the network. For example, a message from Merrill Lynch advertising its Cash Management Account might be targeted to Dow Jones subscribers who regularly look at stock quotes in the data banks. In exchange , Merrill Lynch might pay for a few minutes of the subscriber's sign-on time.

"It's an interesting idea," said Peter Bates, a senior vice president at Ally & Gargano, the New York agency that produces the award-winning Federal Express advertising campaign. "But I'm afraid it might prove to have a high irritant factor. People wouldn't like to pay hundreds of dollars for a piece of software only to find advertising on it."