MCI Communications Corp clearly prefers getting into bed with companies that have near monopolies of their markets, and after British Telecommunications Plc and Rupert Murdoch, it has added Microsoft Corp to its list of partners. MCI’s shares rose $1 to $28.50 yesterday, having earlier hit a 12-month high of $28.625 after it joined Microsoft to announce that each company would sell the other’s products and services, including the less-than- sparkling Microsoft Network on-line service, to business and residential customers worldwide. MCI will provide marketing and merchandising of Microsoft products, billing for the Microsoft Network and crucially, the transmission of Microsoft software upgrades via MCI’s digital network, which will alter the economics of software distribution substantially, to the detriment of retailers. And MCI’s sales force, including that of its just-acquired systems integrator SHL Systemhouse Ltd, will pitch the Microsoft Network to corporate clients. MCI will adopt Microsoft Internet Explorer as its preferred browser software and package it as part of its Internet offering along with other Microsoft products including Internet Information Server and Exchange Server on its internetMCI service. It will market a customised version called MSN from MCI, and the on-line service will provide Internet access through MCI’s Internet network as well as Microsoft Network content and communities, and information on the World Wide Web. And Microsoft has agreed to give its software users access to MCI services through MCI icons on the Windows screen, and will market MCI’s ISDN and other high- speed networking services, conferencing and other offerings, and has also chosen MCI as its telecommunications provider at its professional developer conferences and other events for US software developers.