Is there a limit to how big my video file can be on the DVM7400?

Yes, and no. The DVM-7400 uses a special version of the FAT32 file system, which has a maximum file size of 2GB. This means you cannot directly play a file larger than 2GB in the DVM-7400. However, you can divide this file into several 'chunks' using a file splitting program. As long as those chunks are named properly, the DVM-7400 will treat them as if they were one single file. No playlisting required, and no need to use Play Next. See the Media Files section of the DVM-7400 manual for details.  (Must be using current firmware)