Hi and thank you for using justanswer.
To answer your question;
Press and hold the volume up/down buttons simultaneously for a few seconds on the tv set.
This should remove the store demo mode.
As you appear to be offline i will switch to standard Q&A mode.
We are now in Q&A mode.
I left you an answer in the chat window above.
Hope this help and let me know if you have any questions.
Here is another procedure that might clear it;
Press the volume up button on the tv and while you still have the volume bar on screen press and hold the menu button for 10 secs or so.
If it still does not work then i`ll wait for your model number.
Unfortunately the only other info i got that may be helpful involves the original remote control.
It goes like this; press and hold the exit button on the remote until a screen pops up and ask you if you want to return the set to factory default.
If you want i can help you find an original remote control.
Here is the part number for the remote ; Bn59-00598a
Here one store where you can have it;
I know this is not what you were asking for originally but it may be the only way to reset your tv if unplugging the power for 20 minutes does not work.
Since this is a store demo you may want a owner`s manual , you can find it here ;
Note that on the same page where you have the owner`s manual there is a tab for "Firmware"
That may be another way to reset your firmware to original, some firmware upgrade will reset your tv to its original(Factory default) settings but other will save your current settings.
You will see on this page here that it contains the upgrade file and also the upgrade guide that you should read carefully if you decide to go for the upgrade;
Wanted to thank you for the accept and great bonus.
Also to find out if it was the upgrade that did the trick finally ?