windows 7 laptop hangs at "Logging off"

When I tried to shut down my Windows 7 laptop after installing VLC player, the screen shows "logging off" and just hangs there.

Switch off and re-switch on the PC using on/off button.
The screen showing "logging off" is still there.

Re-switch on the PC several times and it just goes straight to the "logging off" screen.

Could not boot into Windows 7 Safe Mode by tapping the F8 key.

Would appreciate if someone could advise me how to resolve the problem.
I need to use my laptop urgently for an assignment.

Many thanks in advance

Unplug the power supply, take out the battery, wait a minute. Put the battery back in, plug in the power supply, hit the on button and, unless there is something seriously wrong with it, it will boot up.

Thank you so much, jscheuer1.
The problem is now resolved.
You save my day!