Microsoft Corp is overhauling its entire worldwide sales and marketing infrastructure using software from Siebel Systems Inc. Although Microsoft refused to comment on the deal, a spokesperson for Siebel said the software giant was using a number of modules of Siebel’s enterprise management application software: tools that automate sales, marketing and customer service operations. As well as using the software internally, to run its own facility, Microsoft also plans to roll out the solution to its subsidiaries, affiliates and sales partners. This is a very significant deal, said the spokesperson, the fact that a company like Microsoft should chose our software to run its sales and marketing is not only gratifying for us, but also demonstrates Siebel’s strength in the market. This is not the first endorsement of Siebel’s software by a large, international company. Compaq Computer Corp also uses the software to automate its worldwide sales and marketing facility. Other alliances include Anderson Consulting, Citibank and Nationwide Insurance.