How can the two hadiths be reconciled: "O My servants, all of you are astray except those whom I guide" and "Every child is born on the Fitra (natural disposition), then his parents make him a Jew, or a Christian, or a Magian"?

There is no contradiction between the sacred texts, and whoever seeks the truth should gather the texts and consider the sayings of the scholars. The noble hadiths clarify that Allah created His servants upon the fitra, which is the innate disposition upon which people were created, and it is the inclination to accept Islam. However, the devils alter this fitra.

As for the hadith, "All of you are astray except for those whom I have guided," it either means that a person is born knowing nothing, so guidance is the knowledge of the truth and its details, or it refers to the state of people before the advent of the messengers, when they were in a state of Jahiliyya (ignorance). There is no contradiction between these hadiths; for the straying in the second hadith is an aberration that occurs to the fitra.