Sorry to learn this is happening to you. I was not aware of your level of knowledge with computers. It would seem that your data card has become corrupted. You are likely not to be able to retrieve any more files from it.
So, the focus turns to what to do next... First, you can delete all of those files from the computer that cannot be read - they are useless
Next - and you should always do this. Format the camera memory cards in the CAMERA, not the computer. Never just delete your files off a card, as this can lead to a collection of file errors that will create a situation such as this.
The 5D series usually has dual data cards, you should format both of those clean once you have retrieved your images and loaded them on a computer. You should find the format command in the camera's Spanner/Wrench section - location in that group varies with specific model.
Other things to be mindful of. Never turn your camera off or open the card door while the light on the back of the camera is flashing or lit - it means the camera is still saving your images. Always buy data cards from reputable sources - there are a lot of trash counterfeit cards out there.
I hope this helps! If you still have questions, I am happy to help, otherwise: if you are ok with this advise and have no further issues, please mark this thread as resolved, so others won't try to post to it.
cheers, TREVOR
The mark of good photographer is less what they hold in their hand, it's more what they hold in their head;
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
