iTunes Tag doesn't stick?

Hi

I keep my files (movie, tv shows) on a separate hard drive.
When I drop them into iTunes, I tag them (get info, then put the info).
But, they don't seem to stick to the files themselves.
Meaning, if I put them on the iTunes on my laptop, I have to do the same thing over again. Kind of a pain with so many tv series.

So, can anyone recommend a tagging software for videos.

Oh, and i'm using a PC

Thanks

 

I should say that when I input the tags one by one they do show up in iTunes.
My problem comes when I bring that (portable) hard drive and import those files (for the first time) to iTunes and I have to tag them all over again.

The thing is, my notebook has crashed several times on me.
So I'm having to rebuild/troubleshoot it and having to tag all those tv/movies every time get's to be a pain. So, i'd like the tags to stick to the actual mp4 file (if possible).

Now, if I bring the external drive to the desktop, they do show up properly tagged. It's only when I bring them in new.

For my songs, for example, I use Tag and Rename and it sticks to the .mp3 file itself. Everytime I've brought it back to the notebook, it has all the proper info.