For investment managers, the 1990s bull market offered plenty of ways to prosper other than by investing in Internet stocks. One winner: separately managed accounts, or securities portfolios customized by a financial adviser for individual clients, often with securities selection outsourced to third-party managers. So rapidly did separate accounts grow -- from $175 billion under management in 1996 to $425 billion in 2000, according to the Washington-based Money Management Institute -- that some enthusiasts predicted the eventual demise of one-size-fits-all mutual funds.