A friend asked me question and I thought I wrote the solution here, but I’ve checked that out and I see there is nothing here, so this is the problem and the solution.
As you know if you copy the "VIDEO_TS" folder of a region free DVD to your HDD (Hard Disk) you can play the DVD by clicking on "VIDEO_TS.VOB" to play the DVD in "Windows Media Player" and aslo "VIDEO_TS.IFO" to play via "Media Player Classic" both needed to have a compatible DVD decoder like NVidia PureVideo Decoder (or mpeg2 decoder like gabest) (you may see what decoders I use here: http://sadjadbp.spaces.live.com/blog/cns!21F12BB61B822DFA!291.entry) and you will have region problem here.
What if try this:
1) Assuming you have Windows Vista or Windows Server 2008
2) Copy the "VIDEO_TS" folder of a region free DVD to an EXTERNAL HDD (like WD MyBook)
If you try the "VIDEO_TS.VOB" or "VIDEO_TS.IFO" you’ll see a region error like this "Windows Media Player cannot play the DVD because the disc prohibits playback in your region of the world. You must obtain a disc that is intended for your geographic region." but if you copy this folder to an INTERNAL HDD there would be no problem!!!! WHY??? I don’t know, WHAT TO DO??? This is what I know, you have two solutions:
1) Use a DVD player software like VLC Player (which I hate!) that have nothing to do with DVD Region, You may say this is not my king of solution so keep reading No.2.
2) Lets say it this way, I have a folder calls "VIDEOS" which contains of Rock Collection Video DVDs (This is a great collection I have!) on root of my WD MyBook (my External HDD), so I share this folder for my PC User (which is of course THE Administrator) and my computer name is "WIN2K8" so I’ll access my DVDs through "win2k8videos" or you may "Map a Network Drive" for easier access, you may say this is no good enough, so sorry I have no other solutions.
Update #1: I’ve found someone else with same problem here http://www.asciiexpress.com/webguide/forums/Default.aspx?g=posts&t=1712
Update #2: Thanks to Dave (in the comments) yes this would be better, you may use "SUBST" command and that’s better and more easy.
If you found something about this or you’ve tested this and it was helpful, jut leave me a comment.