I have a Hitachi 46 LED LCD HDTV which I have had for several years. All of a sudden the picture is large and stretched. I have changed aspect ratios, etc, but nothing is helping.

You cant change the aspect ratio. You can stretch and zoom programs . Some programs like movies are in letterbox and you can stretch to fill the screen, but the results are not perfect. Circles will be oval and you will cut off some of the viewable picture. This is normal

On your remote control there is a button that controls the aspect ratio on you television. Push the button to change the aspect until you get to the desired ratio.

Check it by changing the aspect ratio to picture. Refer its user manual for details. Gopakumar Gopalan Google

you need to change the 'zoom' on the tv by the remote.
Normal mode frames the 4:3 video to the 16:9 picture area by displaying it in its original aspect ratio, with vertical gray or black bars on both sides of the screen. The disadvantage of this method is the fact that the image is small by virtue of not using the entire width of the screen. This is also known as the 4:3 mode.
Full mode Full mode horizontally stretches the 4:3 video evenly across the entire width of the screen. This is the proper mode to display anamorphic video. If used for standard aspect ratio video, everything on the screen will appear wider than normal. Contrast this with anamorphic video displayed without processing on a 4:3 display, in which people on the screen will appear taller than normal. This is also known as the 16:9 mode.
Zoom mode Zoom mode evenly stretches the picture both horizontally and vertically, until the picture fills the entire width of the screen. This crops out the top and bottom of the picture. This mode is used for letterboxed and open matte video.
14:9 mode Main article: 14:9
In 14:9 mode, the picture is magnified more than in Normal mode, but less than in Zoom mode, while retaining the original aspect ratio.
Wide Zoom mode Wide Zoom mode, also called Just mode, Horizon, or Smart Stretch, progressively stretches the picture horizontally, less in the middle and more on the edges. This allows normal aspect ratio video to be displayed across the entire width of the screen, with minimal cropping, and with much less of the unpleasing visual stretching effect of Full mode.

go to menue under pic setting you should find a tv/ratio setting click on it to change ratio

Your aspect ratio should be at 16:9 for wide screen TV's to get the full picture without stretching it, including plasma, lcd and led TV's. In the older TV's, the aspect ratio should be on 4:3 to get the best image.

Hi,
Press Zoom button on tv remote repeatedly to change screen aspect ratio/ zoom settings of picture that you wish to see.
Thanks.

Aspect ratio is limited by source material. Even if it's set at 4:3, it will still display 16:9 if available such as in movies.

First set your tv to 16:9 aspect ratio. Then go to the source ie: Cable Box or Sat Box. Then go into the User Menu and find the Set Up or HD settings or picture settings. You need to set the Box to the "Stretch" setting. Right now your source box is set ot 4:3 aspect ratio.. If you have difficulty in changing the aspect ratio on the source box, call the Cable or Sat co. They can help you.

This set has several differant aspect ratios, could you have unwittingly change it to a zoom or expand by mistake?