# What algorithm did Windows XP use to choose your initial user picture?

DevFeed: [What algorithm did Windows XP use to choose your initial user picture?](<https://devfeed.tech/articles/what-algorithm-did-windows-xp-use-to-choose-your-initial-user-picture-21759.md>)

Original publisher: [Read original article](<https://devblogs.microsoft.com/oldnewthing/20260909-00/?p=112683>)

Author: Raymond Chen

Published: 2026-09-09T14:00:00Z

Content type: article

Language: en

Sources: [Raymond Chen](<https://devfeed.tech/sources/raymond-chen.md>)

Topics: [Algorithm](<https://devfeed.tech/topics/algorithm.md>), [Randomizer](<https://devfeed.tech/topics/randomizer.md>), [Windows](<https://devfeed.tech/topics/windows.md>), [Filesystems](<https://devfeed.tech/topics/filesystems.md>)

Tags: [algorithm](<https://devfeed.tech/tags/algorithm.md>), [files](<https://devfeed.tech/tags/files.md>), [history](<https://devfeed.tech/tags/history.md>), [old-new-thing](<https://devfeed.tech/tags/old-new-thing.md>), [random](<https://devfeed.tech/tags/random.md>), [recursion](<https://devfeed.tech/tags/recursion.md>), [windows](<https://devfeed.tech/tags/windows.md>)

## AI overview

The article explains that Windows XP selected an initial user picture randomly from the Default Pictures directory using the current time as the random seed. It describes a one-pass reservoir-sampling algorithm, including its efficiency and behavior when files change during selection, with a 100-picture safety limit.

## Source excerpt

It's random, really. The post What algorithm did Windows XP use to choose your initial user picture? appeared first on The Old New Thing.