Seattle: Microsoft Corporation and Nortel Networks Corporation have joined hands in a partnership to exploit the prospects offered by the fast-growing internet telephony market.The two companies said they agreed to a four-year alliance to jointly sell software and services to small and medium-sized businesses, corporations and mobile phone and landline service providers.Canada-based Nortel, the largest maker of network equipment, will work with Microsoft to change its phone systems into software. The alliance will pitch Microsoft in competition with some phone companies.Nortel said it expects more than $1 billion in sales from the new business that will develop software to provide VoIP services. By this, it aims at regaining market share it had to concede to rival Cisco Systems in the $4-billion-a-year corporate web-based phone market. The company is fourth in terms of revenue with a 12.3 per cent market share behind Avaya Inc., Cisco, and Alcatel SA. Microsoft, on the other hand, said it wants to increase its Office business sales. The company plans to simplify the way workers communicate with one another by using software to link phones to computers so that they can handle voice functions. The project visualizes that businesses want products, which allow people to communicate, whatever their location and device they are using.