My Taskbar is missing and I have no Start button - what do I do?

- SOLVED - mysteryious problem
why my taskbar is gone after turn off display

plz remove newest update for microsoft.net framework4 on windows ### (KB2533523) and all of his friend's
100% DONE (I STILL HOPE SO.. :D cikibumm ....)

update answer (i hope so)
THIS TIME ,REALLY - REALLY 100% WORK SOLUTION
did someone knews,
that this problem's occur's/happen only in single user administrator account only?
i knew it, because i have 2 user administrator account and one standard user account
and i have tested it repeatedly
the next clue is: search the programs that using local settigns

then the answer is: go back the time , what program's are you install in past

and finally i found my answer for my question
"why my taskbar is missing after/during turn off monitor,sleep "

this program's i have install is not compatible with win7 "polar clock screen saver"

,maybe someone can found better and quality answer than mine.
thx microsoft for make OS better than before

Thanks alot. I have been having this type of problem and had to restart windows but now, I know that I can just do this step.

I was cleaning my keyboard and suddenly the task bar and tabs all disappeared, and a window I had open was showing full screen. I discovered I had hit the F11 button, and pressing F11 again brought everything back to normal, so you may want to try pressing F11 if your task bar disappears.

I lost the taskbar and when I tried to open Task Manager to retrieve it, I lost that, too! It was only open for a moment then it disappeared - perhaps it somehow was dragged offscreeen? I'm not sure, but lately I've had trouble with my mouse being put offscreen and I have to roll it over the mouse pad for a while to get it back. Maybe that's what happened with the TM. I now have 2 missing things - That are IMPORTANT! HELPPP!

@Christian
When the Task Manager is disabled, it's usually the symptom of a virus.
http://ask-leo.com/why_is_my_task_manager_disabled_and_how_do_i_fix_it.html

One day my taskbar vanished. After a small google-ing i found Christian's post that made the bell ring. My taskbar was on my tv - the second monitor.

OMG thanks alot i had lost all the shortcuts and taskbar,brought it back like Boom!

Had problem with no start menu.
Two bits that helped.
I did not have the run option in TaskManager so created a new shortcut. cmd this created a simple cmd.exe that opened a CMD window to allow me to run programs.
I stopped Explorer process, then started it again but typing explorer in my cmd window.
I still have lots of problems to sort but making a little progress.

The Taskbar with the Start button might be hidden somewhere and you can't see it on your monitor. But if the Taskbar went missing due to virus infection, its difficult to restore it. The virus will also block upgrade installation. The final option is to format your hard drive containing the OS and re-install a fresh one.