Run Windows 95 to XP, Mac OS 8.6 to 10.4 in your browser, sort of
 

Complete desktops contain all operating system components as well as Internet Explorer and Outlook Express. Where possible, I have tried to include built in file transfer programs (Web Publishing Wizard, Web Folders), useful system tools (System File Checker, System Restore) and certain wizards (Network Setup Wizard, Internet Connection Wizard). As a result, some of the desktops are quite large and can take some time to load.

https://www.osnews.com/story/138982/...-your-browser/