Bad Video Quality when playing DVDs

[NXValiant]

Hi,
I have tried to ask this question several times before but never got any satisfying answer, not even from customer support of various companies. This is my problem:
When I'm playing certain DVDs, I get a quite bad video quality. The resolution seems to be 800x600, I don't think it reaches 1024x768. Furthermore, there are blurs sometimes (not always, I find that quite strange) and bright objects (e.g. stars) often shine in different colours, but not white as they should. In fact, this problem only seems to occur when I'm playing DVDs of Star Trek series, but not when playing movies. In another forum, I was told that TV-shows have a lower resolution which would explain the unclear picture I get. However, this doesn't explain the weird stars and blurs.
Can anyone here help me? I just want to watch my Star Trek in good quality

My specifications:
Player: interVideo WinDVD 5 (I also tried it with Windows Media Player and Real Player)
Graphics Card: Radeon X1900XT 512MB
OS: WinXP Home
Monitor: Samsung SyncMaster 930 BF

I also watched some of the DVDs on a normal TV, but there the quality is as it should be, I dont even think there is a low resolution.
Thx for your help

 

[sturm]

How many episodes of ST are there on one dvd? If there is more than 2 then the video quality is probably due to the compresion used to get more than 2 viewing hours on a single dvd.

Also remember that a lcd monitor has a native resolution. Once you get off that resolution, which you will watching a full screen movie, the picture quality drops.

 

[Zoron]

There are 4 episodes per disc... however each episode is about 40 - 45 minutes without the commercials. That works out to about 3 hours per disc... so the compression shouldn't be that bad... especially considering these are television-quality videos. I'm guessing it's more due to the lower res video on a higher res monitor.