The "Big snap" promotion, which was created by Thin Martian, will run 24 hours a day for eight weeks. The push is intended to raise awareness of Microsoft's Live Search and drive traffic to the site.
The six figure marketing campaign encompasses a 12-day broadcast promotion on the Virgin radio network and a week-long print competition with freesheet Metro. A dedicated microsite at BigSnapSearch.com has also been built.
The competition will also be integrated across the MSN network, featuring an online video which will run on MSN Video.
The promotion is based on the traditional card game "snap", with the search results page flashing up matching pairs of cards for prize winners and unlike cards for non-winning searches.
The prizes will be provided by Virgin and include Virgin experience days, Virgin Atlantic flight vouchers and a trip to Richard Branson's exclusive Caribbean hideaway, Necker Island.
Paul Davies, marketing director for MSN and Windows Live, said: "Searching is the second most popular online activity after email and this campaign is designed to enliven people's every day search experiences.
"We wanted to create a really compelling mechanic that would motivate and excite our users while at the same time driving traffic and increasing query volume on Live Search."