Continuing its campaign to boost use of Live Search with cash and prizes, Microsoft has launched SearchPerks!, a search rewards program with an inexplicable Yahoo!-style exclamation point.

Users of Mozilla's Firefox, Apple's Safari, or Google's Chrome browsers are not welcome. To participate, Microsoft Internet Explorer 6 or higher is required.

"Sign up for SearchPerks! and start earning tickets towards exciting prizes whenever you search the Web -- up to 25 tickets per day," Microsoft says on its SearchPerks site. "It's free, easy to use, and your tickets accumulate as fast as you can search.*"

The asterisk indicates that certain conditions apply to SearchPerks. The promotion is limited to the first million U.S. residents, 13 years old or older, with a Windows Live ID, who sign up before Dec. 31, 2008.

SearchPerks lasts through April 15, 2009. That means if you want to earn the 5,500 reward points to trade for the most valuable prize, a video-game controller, you should have joined four days ago.

With the 500 point sign-up bonus that's currently being offered, it will take 200 days, searching 25 times each and every day, to collect 5,500 reward points.

April 15, 2009, the end of the promotion, is 196 days from today, Wednesday, Oct.1, 2008.

In addition to the video-game controller, other prizes include five music downloads (525 tickets), a ball-and-racquet set (750 tickets), T-shirts (1,100 tickets), 1,000 airline miles (1,800 tickets), and a cookbook (3,400 tickets).

"Available prizes may include refurbished prizes," Microsoft's terms of service say. This may be boilerplate that applies to a different contest, however.

Wary of efforts to game its system, as happened with its Live Search Club cash-back promotion, Microsoft is requiring that searches are entered manually "for the good faith purpose of obtaining results for such user’s own research purpose, as determined by Microsoft." As per its terms of service, searches entered by any automated or fraudulent means will be disallowed, assuming such searches are detected.

Microsoft's attempt to increase use of its Live Search service though its Live Search cash-back program appears to be ineffective. Its August search market share in the United States, according to ComScore, was 8.3%, down from 8.5% in May when Live Search cash-back launched.

Google meanwhile has seen its U.S. search market share rise from 61.8% in May to 63% in August.