I assume that you are using some type of software to copy the images and videos to the computer.
Many of these softwares do not handle videos because they were written for still pictures.
If you have a SD card reader on your computer, I advise that you should take the card from the camera and put it in the card reader.
The computer will treat the card as another disk drive.
Then look at the card with your computer and you will find your videos in one of the files on the card.
Copy the video files from the card and put the copy in a Video folder.
You likely already have a folder called "Videos".
If you don't have a SD card reader, you can find them at any store that sells Digital Cameras.
They can be found for under $10.
Displaying video on the camera itself.
If you recorded the video with one of the HD formats (which are wider) they can not fit on the LCD screen unless you have a wide LCD screen. If not, the camera must fit the image within the small screen that is available.
Two things have started happening with my TZ25
1ST when I make a video and try and see it on my computer it does not show up I don't know where it is.
the second thing is before I press the video button the screen shows the full size of the image but when i press the video it narrows down top and bottom I can play it back on the camera and it shows this narrower image, but again it does not show anywhere when i connect the camera to my computer