There are a couple of different ways that the taskbar can disappear or appear to disappear. Naturally, the solutions are different as are the workarounds.
(By the way, I’ll assume that you’re not running Windows 8. That’s a whole ‘nother ball game when it comes to the task bar. )
Press CTRL+ESC. If your taskbar magically reappears, then it’s probably simply been resized too small, repositioned somewhere you didn’t expect it, or perhaps it’s beneath another application that’s running full-screen on your computer.
The workaround? Press CTRL+ESC to access the taskbar.
To fix it, this previous article, “My taskbar is too small to be useful, what can I do?” includes a short video that shows the settings that you can change to make it behave the way you want, and/or the approach to making it “big enough” once again.
It’s not running
If CTRL+ESC didn’t make it come back, then the program that displays the task bar most likely isn’t running. That program is often called the “Windows Shell,” but it’s really “explorer.exe.” It’s the program that not only displays the taskbar, but also responds to the CTRL+ESC sequence.
The workaround: press CTRL+ALT+DEL and select Start Task Manager:
In Task Manager on the File menu, select New Task (Run…). Type in “explorer” and press OK.
That should restart explorer and re-display your taskbar.
In some cases, that may not work, so we fall into the various approaches on fixing it.
Fixing a missing explorer
If you don’t have the Windows Shell running, you can still run programs as I described above: use Task Manager’s File, New Task (Run…) to run the programs we need. I often like to run a command prompt, “cmd”, as a quicker way to type in and run other programs from there.
My first recommendation is to run an up-to-date anti-virus and anti-spyware scan. Both viruses and spyware are known to occasionally interfere with the Windows Shell.
Then, I would run the system file checker, as outlined in this article: What is the System File Checker, and how do I run it?. That will check for missing or damaged files in Windows and repair or replace those that it can.
Finally, you may be faced with re-installing Windows. You can perform what’s called a “repair install” that will preserve your data. This article: “How should I reinstall Windows?” discusses that.
Now, naturally, there may be cases where a specific cause could result in a particular solution. In fact, I’m sure that readers will comment with such various approaches (along the lines of “If you have this virus, all you need do is twiddle that setting.”). Those approaches may (or may not) resolve the entire problem. But if they make sense to you, then by all means, try them out. Back up first!
Microsoft also has a Knowledgebase article on the issue that includes even more steps to try: Taskbar is missing when you log on to Windows.
OK, OK. Windows 8.
The default view is to not have a taskbar, and even when you do, there may not be a Start button. The simplest solution for that is to install the free Classic Shell.