Is it necessary to re-partition the hard drive to ensure the use of an original program, or is that not required?

The question comprised two matters: the ruling on using pirated software without permission, and the ruling on your unawareness of whether the vendor who partitioned your device used original or pirated software. The answer is that you are not obligated regarding the second matter, as it is merely a suspicion. Even if you knew with certainty that he used pirated software, you are not required to re-partition your device; the one who committed the act bears its sin.