PC Week reports that under the terms of the agreement between Microsoft and AT&T, Microsoft will buy $5 billion worth of AT&T securities and warrants. The securities will be convertible into some 66.7 million shares of AT&T — around 3.7 percent of the company — at a price of $75 per share. Microsoft will also get warrants to purchase 40 million more shares of AT&T, which would bring its ownership up to around 5.9 percent of the company. In return, AT&T will agree to use Microsoft’s Windows CE operating system in its digital set-top boxes.