OS-tan or An Anime Girl for Your OS
Ah, Wikipedia. How wonderful are thee?
A small Internet phenomenon on Futaba Channel, the OS-tan (OS for Operating System, and -tan as an overly cute Japanese honorific for a person, specifically a child slurring “-chan”) or simply OS Girls are the personification of several OSes, most famously Windows, by various amateur Japanese artists. A pure fan creation, the appearance of each character is generally consistent across artists. OSes are almost always portrayed as women, the Windows girls usually as sisters, despite sometimes seeming the same age.