Shaurav Sen, 31-year-old CEO of Arlington-based Onscreen Interactive, is the first to admit his idea is simple. He got it last fall when he was looking at a cartoon screen saver on someone else’s PC.

It was a "Sad Sack" cartoon, a childhood favorite for Sen but hardly a harbinger of great things to come. But a seed took root in the technology consultant’s head: What if a business could advertise to customers through changing, interactive but unobtrusive screen savers rather than through pesky pop-ups or banners?

After performing some due diligence and writing a business plan, Sen received his first Angel round of finance in December. Then, in March, he landed $3.5 million in venture capital from Draper Atlantic and Venture Strategy. The idea was also testing well with advertisers and with 60,000 potential subscribers who signed on for free trials at the company’s Web site, www.onscreen.com. "Advertisers were blown away with the concept," Sen says. "A nonintrusive medium on the Internet is so new. Advertisers are feeling the backlash from people who don’t like the pop-ups. It’s a whole new way to reach customers."

The screen savers work this way: If someone calls up the Web page of Sen’s company or one of its advertising partners, he or she can choose to download the screen savers. When the screen is inactive, the new screen savers begin to run, showing anything from movie trailers to short cartoons with an advertiser’s logo. "It works just like a standard screen saver," explains Sen, "only you get to customize the content and see brand new screen savers every day. You can interact with the saver or dismiss it with a single click."

In June, the company changed its name from AdSavers to Onscreen Interactive to reflect a new approach that includes movie trailers, cartoons, flash files, surveys and rewards in addition to traditional advertisements. Instead of pursuing advertisers and consumers, the company now focuses on marketing to existing online communities such as women.com or ESPN.com, which can then sell the new medium to their advertisers to target specific customers.

Sen says that his platform will allow a user to see an ad at least 10 times a day. "By the end of the year, we’ll bring in between half a million and one-and-a-half million in gross revenues," he says. Once the business is in top gear, Sen projects revenues of between $1 million and $5 million per month.

That’s enough to cheer even Sad Sack.