Do you pay attention to the message that appears if you swap DVDs that come from different Regions ?
Here in Australia we have Region 4 DVDs but many people have DVDs from Europe ( Region 2 ) and the United States ( Region 1).
Most computer DVD drives will allow only 4 changes to the Region before locking the drive to that Region.
You will then be stuck with say Region 2 to play your DVDs on that drive.
What can you do?
Well formatting the hard drive and reloading Windows will make no difference.
You can Google the problem and see if there is software that will enable you to "Flash " your DVD drive so that it can play all Regions with no change reminder.
You could try installing VLC which may play the DVDs
The last fix is to install a new DVD player in your computer.
An expensive solution to not reading the warnings.