I have the same problem, The power dvd software my computer came with is corrupted somehow now and I cant get it to work. Going to their site is worthless and patches didn't help.
I just found the ati dvd decoder and that solved my problem. Although you have to have a ati card and the original install/drivers cd.
I imagine other makers have the same support for dvds, you just might have to look for it.
Just search for it.