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Could you check if there are any executable files on the flash drive? Their .mev format is proprietary which will only play with the player software on the flash drive itself.
In case the files are just hidden, when you go into the flash drive, go into the “Tools” menu and then into the “View” tab. Tick the options “Show hidden files and folders” and remove the tick from “Hide protected system files” and accept the warning.
Another thing worth noting is that Microsoft has disabled AutoPlay in Windows 7 and in an August update for XP & Vista (some info here), so if you are running Windows 7 or have installed this update, the AutoPlay functionality will not work. In this case, you will need to try finding the executable file on the pen drive. It’s most likely the name of the movie as the user above has noticed on their pen drive.