You can use your digital download code on two separate computers, but only if they are not running at the same time. So you could have X-Plane on your desktop at home and on your laptop for when you travel with no problems. Our piracy check may be alerted if you are using the same code at the same time on two different computers. We have this to prevent someone from stealing your code. If you try to authorize the digital download code and it doesn't work, you can send ONLY the last 8 digits of your product code to info@x-plane.com and they will look up to see if you have been locked out.