Is it permissible to use pirated operating system discs to install them on customers' devices after formatting them, and is the money earned from that permissible or forbidden?

It is not permissible to copy discs whose owners have not given permission for their duplication. This is to uphold the right of invention, which is a recognized right, and to adhere to the agreed-upon condition. It has been stated in the fatwas of the Permanent Committee for Issuing Fatwas that it is not permissible to copy programs whose owners prohibit their duplication except with their permission, based on the Prophet Muhammad's (peace be upon him) sayings: "Muslims are bound by their conditions," "The wealth of a Muslim person is not lawful except with his willing consent," and "Whoever precedes to something permissible has a greater right to it." This includes the right of a non-belligerent disbeliever, which is respected just like the right of a Muslim. Sheikh Muhammad bin Salih Al-Uthaymeen (may Allah have mercy on him) was of the view that the matter follows custom; if the owner explicitly prohibits both private and public copying, then it is absolutely not permissible. However, if the discs belong to a company from a state that is at war with Muslims, then there is no harm in copying them.