For a long time, some Microsoft officials have privately griped that PC makers don't present Windows in its best light. They clutter desktops with icons that are often little more than ads for third-party products; include confusing utilities that duplicate functions already in Windows; require lengthy setup; and configure PCs in ways that slow them down.

One consequence, in the eyes of these Microsoft executives, is to confer an advantage on the company's main operating-system rival, Apple.

Now,...