«...but there's a law that says if you receive something in the mail that you did not order, you're not obligated to pay for it and you can keep it»
That's not exactly true. You are not obligated to pay for something that was shipped unsolicited but you cannot keep it if it was sent to you in error and the vendor notifies of the error you in a timely manner -- so they should put the two disks by the door and give them to the Staples driver when he comes to collect them.
That's not exactly true. You are not obligated to pay for something that was shipped unsolicited but you cannot keep it if it was sent to you in error and the vendor notifies of the error you in a timely manner -- so they should put the two disks by the door and give them to the Staples driver when he comes to collect them.