Microsoft and Dell are the latest companies to have signed up to Product Red, the brand launched by Bono, the rock star, to raise money to combat killer diseases in Africa. The collaboration will involve Dell producing two laptops and a desktop computer loaded with Microsoft's Windows Vista operating system. Between $50 and $80 from each sale will go to the Geneva-based fund to fight Aids, tuberculosis and malaria in the developing world.

Alan Beattie, London