Hewlett-Packard Co. said it agreed to buy networking-gear maker 3Com Corp. for $2.7 billion in cash, the latest move by H-P to bulk up its product line amid a broader push by the few remaining technology giants to turn themselves into one-stop shops for corporate customers. The Palo Alto, Calif., company—the world's largest tech company by revenue—also preannounced positive fiscal fourth quarter results. It posted an 11% jump in operating earnings and an 8% decline in revenue from a year ago, beating analyst estimates. In a sign the tech industry is leaving the recession behind, H-P also raised its revenue forecast for the new fiscal year. By buying 3Com, a onetime leading tech company that has fallen on tougher times this decade, H-P is aiming to goose its growth. The move also puts H-P more squarely on the turf of Cisco Systems Inc.