dark image with DVD's

Hello,

I have a problem playing dvd’s with my computer. When I play any DVD, the color looks fine until the movie comes to a scene with low light, like in an alleyway or at night. Then the movie is so dark that I can’t make out what is happening. This problem only happens with DVD’s. My computer plays all other video files perfectly. I have a Pentium 4 with windows XP and an NEC monitor. I have just downloaded all the new windows drivers but the problem persists. I have tried adjusting the settings on my monitor, but that doesn’t help. Any ideas would really be appreciated.