Smartphone videos upside down (after I put them on my laptop computer)

I have a samsung express 3 ,when I first got it I tested the video camera a little bit with no problems.

Today I filmed 2 videos and one of them is fine but the other looks normal only on the smartphone screen but when I put it on my laptop it is upside down. After that I did some test videos and a lot of them come out upside down when I save them to my laptop and watch them on vlc.

(This problem is frustrating because I like saving my videos and photos to flash drives and my computer so I can keep them.)

1-Why is my smartphone doing this?

2-Is there something I can do to make the smartphone stop doing this or am I just going to have the fix the videos every time they do this?

3-If this glitch is unavoidable then What's the best way to to rotate the video file back to normal on a computer?,How do you fix the problem on a computer?

Maybe the gyroscope needs calibrating. The phone might think that it's left side up in landscape when it's actually right side up.
So because it's only once in a while it happens to you, i imagine that the Yaw axis (or pitch when in landscape) is about 90 degrees wrong.
So it's right there on the edge to be one side or the other when you hit record. Just a theory

Check this link out for methods on how to test and fix it. (Given the gyroscope is the problem)
http://www.wikihow.com/Calibrate-the-Gyroscope-on-a-Galaxy

Update: I think I figured It out.

Even though it always looks normal on the smartphone screen, If you film with the volume buttons facing down the video will be fine but If you film with the volume buttons facing up
the video will be upside down when you put it on the computer. Even though it rights itself for viewing on the smart phone screen ,the incorrect orientation of the smartphone itself during filming was what was causeing the footage to be upside down when veiwed on a computer.

This was out of left field.

I have this issue with my Seekthermal. I just use Wondershare video editor to flip the video back to normal.