Is it permissible for me to activate all the features of a government-issued computer for an employee belonging to a government entity?

You did well in not helping the man, because the employee is entrusted with what is under his authority, and it is not permissible for him to overstep what was agreed upon between him and the employer, either explicitly or implicitly by custom. This is based on the Prophet's (peace be upon him) saying: "Muslims are bound by their conditions, unless it is a condition that prohibits what is lawful or permits what is unlawful." If he is explicitly instructed to refrain from something that is permissible by custom, then he must comply, because a custom that holds the status of a condition is abrogated by an explicit statement to the contrary, provided that it is permissible by religious law.