ReactOS: Open Source Windows OS

Overview

• Video demo and review by ExplainingComputers, walking through ReactOS v0.4.15 (released March 2025).
• ReactOS is an open‑source reimplementation of the Windows NT family, aiming to run Windows applications and drivers without any Microsoft code via clean‑room reverse engineering.

Key technological concepts & project status

• Goal: binary/application and driver compatibility with Windows NT, with a focus on older/classic 32‑bit Windows applications.
• Legal approach: entirely original code through clean‑room reverse engineering.
• Architecture and builds:
  • 32‑bit builds are the mainstream public downloads and the recommended channel for general testing.
  • 64‑bit builds exist but are experimental; they currently lack a compatibility layer to run 32‑bit Windows software (no WoW64 support).
• v0.4.15 notable improvements:
  • Plug‑and‑play subsystem rewrite
  • Audio support improvements
  • Memory management and cache control updates
  • Registry healing/caching
  • Security enhancements
  • System tools and accessories improvements
  • Shell refinements
• Status: still alpha. Considerable progress compared with 2018, but incomplete and can be unstable in some areas.

Downloads & media

• Official downloads are available from the ReactOS project site, with links to SourceForge and nightly builds.
• Available images include live CD images suitable for USB boot and boot/install images.
• Live images are useful for testing on real hardware but compatibility is limited; ReactOS maintains a list of known‑compatible systems.

Compatibility & hardware notes

• Works better on older or lower‑spec hardware; many modern Intel systems may fail to boot the live USB.
• The project provides a hardware compatibility webpage (mostly older devices).
• Recommendation: use 32‑bit builds for general testing; 64‑bit builds are for experienced testers only.

Walkthrough / installation guidance (demonstrated)

• Creating a live USB:
  • The reviewer used BalenaEtcher to write the Live CD image to a USB stick.
• Virtual machine recommended for fuller testing; the reviewer demonstrated an install in VirtualBox.
  • VirtualBox notes: some versions (6.1.44 → 7.0.14) have known issues; the reviewer used 7.0.16+ successfully.
  • Recommended VM configuration:
    • 1 CPU core (ReactOS recommendation)
    • Up to 4 GB RAM (32‑bit limits)
    • Small virtual disk (10 GB used in the demo)
  • Simplified install steps shown:
    1. Boot the ISO
    2. Format and install
    3. Remove the ISO on reboot
    4. Complete setup (user name, password, appearance)
  • VirtualBox tips:
    • Increase display scaling (e.g., 200%) for readability in video demonstrations.
    • Install VirtualBox Guest Additions for correct display resizing and improved integration.
• The reviewer demonstrated mounting ISO files inside the VM to install Windows applications (for example, Microsoft Office XP).

Bundled software & application compatibility tests

• Bundled applications include:
  • A basic web browser (“Wine Internet Explorer” using shared resources with Wine)
  • Utilities: Notepad, Paint, WordPad
  • Games: Solitaire
  • Applications Manager: category catalog for easy installs
• Applications tested by the reviewer:
  • Microsoft Office XP: installed successfully; Word, Excel, and PowerPoint worked. Access produced errors when creating a blank database.
  • Adobe Audition 1.5: installed and played audio successfully, demonstrating the audio subsystem functioning.
  • Blender (an early Linux/graphics port listed under Graphics): an early build ran but showed graphics errors.
  • Web browsing: simple pages load in the bundled browser; complex sites (e.g., YouTube) do not render properly.
• Summary: application support is promising for many 32‑bit Windows desktop apps but is not yet comprehensive.

Stability and limitations

• Stability has improved relative to earlier versions; the reviewer did not see crashes during many app installs in this session.
• Remaining instability:
  • Heavy crashes occurred when attempting to install a tablet driver and during device manager exploration.
  • Driver model and hardware handling remain fragile.
  • Graphics and some driver support are limited; expect gaps and instability, especially with newer hardware or complex drivers.

Reviewer analysis / conclusion

• ReactOS shows significant progress and potential as a niche OS for running legacy Windows apps on open‑source software.
• Best current use cases:
  • In virtual machines on modern hosts
  • On older, compatible hardware for testing
• Not yet ready to replace a primary OS.
• Development trajectory is encouraging, and further improvements are expected as the project matures.

Practical items demonstrated

• Creating a ReactOS live USB with Etcher
• Booting live images on real hardware and checking the compatibility list
• Installing ReactOS in VirtualBox (VM creation, recommended settings, format/install sequence)
• Installing VirtualBox Guest Additions for better display integration
• Mounting ISOs and installing Windows applications (Office XP, Adobe Audition, Blender)
• Using the built‑in Applications Manager to install apps

Main speakers / sources

• ExplainingComputers (video presenter / host)
• ReactOS project (official website / SourceForge / nightly builds)
• Wine project (shared resources; Wine Internet Explorer browser)
• Tools & platforms referenced: BalenaEtcher, VirtualBox (and Guest Additions), SourceForge, Microsoft Office XP, Adobe Audition, Blender