You can't transfer from the PS3 to a PC because, as already said, the replay file simply contains the data to reconstruct a replay from the game resources. Only the PS3 can do that.
You can transfer from a video capture device to a PC or Mac.
The types of device range from simply using the camera on your mobile phone, the movie function on a digital camera (I do this for quick stuff) or a dedicated video capture device that is capable of slotting between the Video Out of your PS3 and the Video In of your TV.
Use your favourite search engine to find more details of these devices and to see what's suitable for your own region and setup.