Question [Q] Sony Xperia Z video transfer problem

Hi there,
Forgive my ignorance but I need help! Yesterday I took some great video footage and went to transfer them to PC this morning in the normal manner that has worked many times previously. Let me add that the videos played back just perfectly on the phone, HOWEVER when I then transferred them to PC, all of the files show, but only 2 will play back, the others are just BLACK. Nothing can be seen. I would DESPERATELY like to somehow get these files back!!! Stupidly I recently changed my file transfer settings to delete files after transfer because I have had no previous problems so now the files are gone from my phone Would you know if there is ANY WAY I can get these files to play?
Any help is greatly appreciated.
Cheers, Sharon.