“Guitar Hero III” is rocking out to boffo sales. Activision revealed on Monday that the latest installment in its popular music videogame franchise grossed over $100 million in its first seven days on sale in North America. That appears to make it the second biggest videogame of the year, far behind Microsoft’s “Halo 3,” which grossed $170 million domestically on its first day alone.

“Guitar Hero III” has a somewhat easier task, however, since most gamers buy the guitar controller along with the game for a combined price of $100. The standard version of “Halo 3″ costs $60. Success of “Guitar Hero III” raises questions about how MTV’s “Rock Band,” a similar game from the developers of the first two “Guitar Hero” games, will perform when it comes out later this month.

Perhaps players won’t have money left to buy the even pricier “Rock Band,” which also has a drum set and microphone; on the other hand, the “Guitar Hero III” perf may be a sign that the overall music vidgame space is booming. News came as Activision reported boffo results for the quarter ended Sept. 30. Revenue grew 69% to $317.7 million from a year earlier, and the company swung to a $700,000 profit from a net loss in the quarter last year.

Solid performers included the “Transformers” movie adaptation and “Guitar Hero II.” Sales were particularly strong overseas, where net revenue grew 80%. Activision’s perf stands out against competitors like Electronic Arts and THQ, which saw revenue drop last quarter ( Daily Variety , Nov. 2).