Problems Reading Original DVD on my PC

[The Keeper]

I'm experiencing a problem running my originals dvds on my pc.

I have a lg 16x dvd reader but i'm able to read just few dvd of my collectiong because often i recive an error message who tell me that the protection in the dvd disc do not allow me to reproduce the movie on a pc. I hope that this will be a problem related to my pc or dvd reader or dvd software (actually i'm using Powerdvd) cause otherwise we're facing a violationg of our right of reproduce the original dvds we buy wherever we want in the respect of the copyright law.

As further info i can tell that my OS is WinXP and my PC is a PIV with 521 MB RAm and a geForce4 with updated driver and DX9 Installed
I hope someone of you can help me

Thanks in advance
THe Keeper