Michael Dell could make his mark in the financial world, too. MSD Capital, the firm that manages more than $10 billion of the computer billionaire’s money, is opening a $500 million European fund to outside investors. It’s a philosophical shift. If investors buy in, MSD is already big enough to be a ready-made alternative investment powerhouse. The biggest firms with funds open to the investment world at large — some of them now publicly traded — run several times as much money as MSD. But even as the firm stands, it might make it into the top 25 or so managers globally. It has already been involved in private equity deals alongside better-known investors such as George Soros and John Paulson.