SAN FRANCISCO (MarketWatch) -- When Microsoft Corp. delivers a mysterious prototype for government testing this coming week, it will mark a crucial juncture for a high-stakes bid to change the way consumers get their Internet access. That bid has cast Microsoft and a group of powerful allies from Silicon Valley in the relatively unfamiliar role of Washington policy players. Microsoft's prototype, delivered on behalf of the group, is a wireless device that could provide the public with free and more widespread access to the Web instead of relying on networks owned by big telecom and cable firms. That breakthrough,...