This site is being deprecated.
Please see the official X‑Plane Support page for help.
Unlike Thomson I am not with Laminar Research; just a flight simmer.
For starters follow Thomson's advice but you also need to ensure you are installing as the administrator and you may need to ensure your antivirus etc software is temporarily disengaged. This action should/may find corrupted files and replace them.
If this fails perform a complete deletion of X-Plane a start again.
There is no product or password key for a disc version whether it be XP10 or XP11.. Disc 1 has to be installed in the hard drive at all times. Any product key you think you had for X-Plane would have been a password from the creator of the disc set as a ploy to get you to purchase more of their products at a discount rate. Initially I was caught the same way with my XP11 installation.
However there is a saving grace with XP10 whereby you can use a USB dongle as a substitute for XP10 disc 1. Details can be found here at https://www.x-plane.com/product/x-plane-10-home-use-usb-key/
This site is no longer being actively maintained.