Yup, once you flash hard spl, you don't need to do it again.
To play videos on your pc, you have to plug in your usb cable to your phone and the pc.
Depending on where the files were saved, you should select either Activesync or Disk drive on your phone (there should be a prompt on your phone as soon as you plug your phone in to your pc).
If your files are saved in your storage card, then I would suggest Disk Drive.
Otherwise, sync your phone through Activesync and look in My Documents.
Once you find your file, just copy it over to your pc and play it.
If you have any issues playing the videos, just download and install VLC media player.
That should do it.