can't play commercial DVD on notebook

[sender]

I rented some commercial DVDs. They all can be played on my mother's standalone DVD player. But when I take them back home and play on my IBM notebook PC with WinDVD, some of them played fine, but for others, the software complainted that they are not video disc. I have checked the region code of this discs and they are for all regions. So it should not be the region restriction. Could it be other kind of anti-priate measures that prevent PC or notebook to read the disc? If so, it is unfair for me as I use legally rented disc and legal software to play them. I should be entitled to enjoy what I paid for. I just don't have a stand alond player. Is there any software I can use for these discs?

[ormonde]

Try "Cleaning" the problem DVDs.