How to rotate 3GP video from 'landscape' to 'potrait'?

I've been taking videos on my SE K550i phone on 'landscape' unknowingly. I only know today that I can't rotate the original 3gp file to 'portrait'.

So, did a bit of research on Google. Thankfully, there are solutions.

Firstly, download the free 3GP video converter here.

After that, import the file into the Window Movie Maker, drag a clip and dropped it on the timeline. Then, select 'Rotate 90' in 'Edit Movie' step. Lastly, save it!

Presto, you now have your video converted and rotated!