The instructions on how to remove the region restriction, was actually in the box with my DVD player. It involved about 20 presses on the remote control. If you didn't get this with your DVD player, then they are easily available on the web, as previously mentioned.
The only issue is that it potentially invalidates your warranty. That said, I have never had a problem with my DVD player. If you do have an issue with your DVD player, you can always make it single region again. DVD players are so cheap nowdays, that I would probably buy a new one, instead of bothering with a warranty.
I have never thought about whether PC DVD players are single region. I have never noticed on my previous PC's and laptops, so I would suspect not. If they are single region, I am sure that a solution could be found on Google pretty quickly.