Transferring from external hard drive

Not sure if this is the right category, but seemed to fit enough.

Got an external hard drive. Bunch of movies and everything on it. Initially put on there from my desktop. Went to put them on the laptop hard drive since can't always just have the external one with me when I'm out.

So, I set it to transfer a couple seasons of a TV show. Gets about halfway through and tells me that it can't locate an item. Well, I go through, verify the hard drive is still connected, both by checking the cord, and checking the "My Computer" section. It's connected. Checked the file location. The file does in fact exist. I tried manually moving that specific file by itself. Same thing.

Tried to play the file from the external hard drive just as a test. Would not play. Said there was some error and unable to play, and no image was displayed for the icon when sitting in the folder (Like the initial preview of the file).

Hooked the hard drive up to my desktop. Moved the file onto the desktop computer no problem. Was able to play without any problems.

Ideas? Its an .avi file, so I'm not really sure why it's an issue. Pretty sure my codecs are fine, but even with that, shouldn't affect being able to move it onto the laptop.