The simple answer is, without a lot of messing about, you can't.
The camera requires a specific number of files in a particular structure to replay a single clip of footage. When you transfer those files to a PC, the computer has its own requirements, and the necessary conversion, even unedited, renders the movie incompatible with playback on a camera.
While I think it may be technically possible to recombine a converted file into the required file structure, I know of no documentation or 'formula' that might help you do it and a quick search around the 'net shows that's the case with most cameras.
As far as I'm aware, only an exact copy of the original SD card contents (and file structure) can be re-copied back to the card for replay on the camera. If you back up your card in this way as well as uploading/converting to your PC, you may be able to achieve what you're asking here.