American lawyers are to file a lawsuit against the computer company Microsoft today, in the first of what legal experts say, could become a flood of private litigation, stemming from the US Justice Department's action against the company. Earlier this month, a judge found that Microsoft was a monopoly whose anti-competitive acts had stifled innovation and harmed consumers. The action accuses the company of using its monopoly in the field to overcharge buyers of Windows 95 and Windows 98.