boxelder – which software are you using to edit the footage on ?
If you’re using Final Cut Pro, you can use the log and capture window to import the footage, and then export it back out as something more web friendly for upload to YT.
If you’re using Adobe Premier CC they should be able to be imported straight off from the Master file.
imovie supports the AVCHD codec as well.
As for moving the file onto your computer from your camera, I’d strongly recommend transferring the entire file structure, and not just the video files from the sub-folders, as there can be metadata which is encoded, which you will need for editing. In other words drag and drop the folder marked PRIVATE (and all the sub-folders it contains), and then re-name it so you can find it later on.
EDIT : Also, sack off Windows Media Player as it’s ****. Download VLC Media Player, and use that instead if you want to just play back any files.