Picture too big for screen

Press the Format button. It's directly below the power button. It has a symbol of a rectangle with a double-headed arrow inside.

Press it to cycle through the different picture shapes.

Posting the model number would make a response more valid but you need to go through the main menu selection and check to see if you can alter screen resolution or geometry there.Most sets offer different views such as 'Panorama,' 'Full screen,' etc.

Go to the picture setup of your settings menu.
Somewhere in there are options for selecting picture size.
The options will be similar to: Normal, Wide, Zoom, Stretch
You have probably selected Zoom, try Normal.

Change the aspect ration in the picture menu for a different apperture.
Hope that helps.

crop the picture edges using photoshop

If you are tuning from cable or satellite you need to change the settings in the picture menu look for options like "stretch" "autofit" etc. cycle through until desired picture is displayed, turn off widescreen setting if you can find it check the manual for options regarding this. If you have it attached to a computer you will need to change the resolution to something smaller like 1366X768 which is the standard 720p resolution for the smaller tv's If there is still a problem it may be

Check the menu settings for the picture. You may be expanding the image to fill the sides, in the process, cutting the top and bottom.

type in PT-47WX51 manual in your search bar and there is an online manual from fixya. It will take you through setting up your tv.

HDTV's come with selections that will change the screens display, on the remote press the format button and you should be able to find a setting that you desire.

If you mean that a black box appears on the screen, and you can still see the picture around the box, it means that your closed captions are on and set to TEXT. If this is the case, enter the menu, navigate to the closed captions page and set the captions to OFF. If you mean that the top of the picture has collapsed down, the vertical circuit has stopped working correctly and the set should be serviced by a qualified tech.