OAK BROOK - McDonald's Corp. on Wednesday held Webcast touting its "biggest, best actuation" this year for the 2008 Summer Olympics in Beijing. It declined to say how much the Oak Brook-based firm is spending but company officials highlighted a host of marketing initiatives, including the alternate-reality game called The Lost Ring, which McDonald's said is the largest such game ever played. A joint McDonald's and Beijing Olympics site, The Lost Ring is being played by two million participants worldwide, McDonald's said.