Microsoft co-founder Paul Allen has died aged 65 from complications with non-Hodgkin lymphoma. He was first treated for the disease in 2009 but it returned this year. A childhood friend of Bill Gates, the pair started Microsoft in 1975. Allen was also an avid sports fan and went on to buy several sports teams. He was ranked among the world's wealthiest individuals, with an estimated net worth of more than $20bn, and dedicated much of his later life to philanthropic work.