IBM has appointed Virginia Rometty, the company’s current head of global sales and senior vice president, to be chief executive in 2012, making her the first woman ever to lead the legendary U.S. computer technology company. Rometty, 54, will take over for Sam Palmisano on Jan. 1, who will remain chairman of the board of directors after heading the company for more than a decade. Rometty's new role at IBM makes it the largest U.S. corporation by market value to be headed by a woman. (IBM is also known for its eco-friendliness, coming in at No. 1 on Newsweek's 2011 green rankings.) She joins a select group of women at the helm of U.S. tech companies, including Meg Whitman, the former head of eBay who was recently named CEO at IBM’s biggest rival, Hewlett-Packard.