Saudi IT firm Wamad is behind the venture - called Media 20-20 - which will see ads being targeted at PC users according to their demographic status.
The initiative is linked to the Saudi government's home computing project, which is aiming to increase internet penetration and PC usage in the Kingdom.
The service will be formally launched at the Gitex IT exhibition later this month and is expected to begin operations on 1 January next year.
Using technology that is used to control corporate computers, Media 20-20 will replace screensavers and wallpapers on each participating PC with ads.
People who want to take advantage of free internet access will be required to complete a registration form.
Moses Kuria, chief operating officer at Wamad, said: "Using our technology, when somebody hooks up to the internet we are able to control their computer in the same way as we control it through the corporate network. That means that we are turning the computer into media."
Kuria said he was consulting with advertising and media agencies in Saudi, including Saatchi & Saatchi, to check the viability of the project.
"Today you have to go to websites to get the adverts. With our technology you don't have to go to any websites, as long as you are online," Kuria added.
"We have a specific technology that's able to submit the content according to the profile. A doctor might see adverts for Johnson & Johnson, and a builder might see adverts for building materials."