People will treat it as a normal part of using your software and they will ignore it. Do not dismiss the payment request message through a keyboard button press. Pressing that button could be automated. Instead, swap buttons around, make them read the buttons and press on the correct one with their mouse. Do not tie your software to someone's hard drive parameters.
People reformat their hard drives, they upgrade to larger disks, sell their machines, etc.
You will do lots of support for legit users every time there are changes to their hard drive. Do not threaten to erase their hard drive if they are using a known pirated registration code because you will get blamed for the next bad thing to befall their computer. Do keep track of the published public rgistration codes and in future revisions, disallow these registration numbers. Do check for registration code validity in several places in your code and only enable some of these various checks on, for example, odd weeks or even months. If someone publishes a patch for your software, it will work until the next month and then it will cease to work.