The number of people who have been able to use a RealSense camera with Windows 7 is very low, as it was originally designed for a minimum of Windows 8.1. There have been a few who claimed to have done it though.
I could not locate a Debian version of the original Librealsense 1.12.1 but there are apparently Fedora Linux versions.
You do not need to register the camera's serial number. The serial that the old SDKs refer to is one emailed to you when you fill in a registration form. You can bypass the serial and download the 2016 R2 SDK directly with a link on the page below.