Final answer:
The sentence is in passive voice because the subject of the sentence, the operating system, is receiving the action of being downloaded, rather than performing the action.
Step-by-step explanation:
The sentence "By now the operating system should have finished downloading to my computer." is written in the passive voice. In this sentence, the operating system (the subject) is not performing the action (downloading); rather, it is receiving the action. The hallmark of a passive voice construction is that the subject is being acted upon, often identified by a form of the "be" verb (in this case, 'have been') followed by the past participle of the main verb ('downloaded'). In contrast, an active voice sentence would place the subject as the doer of the action, such as 'The computer has downloaded the operating system.' where 'the computer' is the subject performing the action.