A site spotted by The Next Web allows you to use Windows 95 in your browser, thanks to the power of Javascript and emulator software Emscripten and DOSBox.
To try it head out, head here and click the 'Start Windows 95' button. Be warned the disk image is 131MB uncompressed, so it will take a few minutes to load on an average connection, and even once loaded, it will probably run slower than you remember for a variety of technical reasons. Once you're in, click the Fullscreen button to gain control of the OS.
Windows 95 launched 20 years ago and was a landmark OS for Microsoft. Support for it ended just a day prior to 2002.