I talk 14-6 The past perfect  should be used to describe an action already completed by the time of another past action . The simple past tense  should be used to describe a past action that took place at the same time as another past action . The perfect infinitive should be used to describe an action occuring earlier than the main action in the sentence . This sentence combines the choppy sentences by making a subordinating clause, that claims to be user-friendly. But the placement of the clause makes it seem to describe the computer, not the manual. The word Although doesn’t make sense in this context. Although means "in spite of the fact that.