RetroBar is an open source tool that changes the taskbar's appearance to that of Windows 95, 98, 2000, ME or XP
Which version of Windows did you use first? The first one I tried as a kid was Windows 3.1. I consider myself lucky to have experienced the evolution of the operating system, from Windows 95,98, XP, Vista, 7, 8/8.1 to Windows 10.
If you have never used one of the older versions of the OS, or if you're feeling nostalgic about them and want the old UI back on your Windows 10 computer, you may be interested in RetroBar.
The freeware tool replaces parts of the GUI to give it a retro feel, hence the name. The program is portable, extract it and run the executable. Your taskbar will disappear, give it a few seconds and a different bar takes its place. This is the Windows 95 taskbar. Windows 98 had the same interface. It's not just the task bar, RetroBar also modifies the system tray and the start button for uniformity.
The program retains all your taskbar shortcuts, which is helpful. Right-click on a blank area of the taskbar, and RetroBar's context menu will pop-out. Use it to access the Windows Task Manager, or to toggle the clock or the quick launch icons. There is a much cooler option here, the theme drop-down menu.
Click on the menu, and you may choose any of the following options: Windows 2000, Windows 95-98, Windows ME, Windows XP Blue and Windows XP Classic. RetroBar doesn't waste time when switching between themes, the change happens instantly.
To close the program, select Exit from the right-click menu. Surprisingly, it exits (and opens) without restarting Explorer, which probably means that it uses an overlay over the default Taskbar.
RetroBar is an open source application written in C#. I think it's worth mentioning that the program does not alter the appearance of the Start Menu, you may want to look into Open Shell for an XP styled skin. Advanced users maybe interesting in customizing the program's theme. To do so, you will need to create a folder in the program's directory, and an XAML file. The project's GitHub repository has XAML files for the built-in themes, that you can use for reference.
Windows 10's tray icons (Wi-Fi, speaker, battery, etc.) appear too thin and faint, but we can't really blame the tool for that. However, the default icon size on the taskbar is way too small, the program needs to offer a way to resize them. Windows 10 avoids creating labels on the task bar for programs that are running, it uses icons. RetroBar does not support this, and as a result your taskbar could get cluttered really quickly. Look at the first screenshot above and the one below from Windows 10, and you'll see what I'm talking about.
RetroBar hides nearly all options of the Taskbar's context menu, which makes it a bit inconvenient to use. You can't access the Action Center or use the Show Desktop button. The fly out menu (right-click menu) for taskbar icons, and task preview are not available either. And, if you're using custom toolbars like the Everything Toolbar, you can't access any of those. On the other hand, notifications work fine.
I think Windows XP Blue's taskbar, start menu and tray still looks the best. What about you, which one do you like?