[RachelF]

It's called the registry. A very long linked list data structure designed to scare experts into using another OS. This process takes time as despair finally wins against hope.

[layer8]

The registry is not that different from a file system, actually. It even allows mounting other “file systems” (registry hives).

[ratsmack]

And over time, it becomes a huge garbage dump that slowly degrades the performance of the computer.

[Zuider]

But the festering garbage is entangled with essential material so that attempting to take out the trash can brick the OS.