In an effort to increase operating system stability, Microsoft determined that in Windows 2000 and all future operating systems, print drivers would run as user-mode processes. User-mode drivers run in a protected part of the operating system, as do all of the normal end-user processes and software programs. A user-mode print driver that functions incorrectly can terminate (or “crash”) only the process in which it is running—not the whole operating system. Because access to critical system resources is restricted, overall operating system stability is increased.

ENWW

General Microsoft Windows installation instructions 77