Hello Essence10,
Thanks for your update.
If you have the original file on an SD card, I would suggest saving it to your computer, possibly in the Movies folder. Then, in iTunes for Windows, select File > Add to Library from the Menu bar.
iTunes 12 for Windows: Import music and video already on your computer
To delete the version of the video that you currently have in your iTunes Library, follow the steps below:
iTunes 12 for Windows: Delete songs, playlists, or other items
Delete an item from your library
Click the item to select it, and press the Delete key.
Click Delete [item].
Do one of the following:
Remove the item only from your iTunes library: Click Keep File.
Delete the item from your computer: Click Move to Recycle Bin. The item is removed the next time you empty the Recycle Bin.
Since you are using a Windows computer, you may have your own strategies for backing up your data. This resource will provide specific instructions for backing up your iTunes media library:
Manage and back up your iTunes media library
Enjoy the rest of your day!