Best practices for working with a new computer

What steps can I take to detect if a brand new computer has been compromised?

Would it take an actor with significant resources to compromise a system and still have it appear to start the standard Windows set up wizard? Partly I ask this because I wonder if reinstalling the operating system would help or if anyone who could compromise the system in this way could also compromise it (through the BIOS) such that a reinstall would still not help.

I ask because I just received a brand new laptop in the mail that arrived in a box with the only seal compromised (i.e. I could open the box and remove the laptop without cutting any tape or breaking any seal). I tried to ask a question in the least subjective way I could but please comment if you can suggest a less subjective form of the question or can recommend a better forum asking about this than Stack Exchange.