DVD playback bad picture.

[Dash]

Hi.
I have a problem with a new PC not playing back DVD movies properly. The display works normally in all aspects except DVD playback, where the picture looks almost like a color negative with the brightness turned way up. I've listed my system configuration below as best I can. I can't think of any reason for this happening, but maybe someone else has had a similar problem.
Thanks,
Dash

Motherboard: PC Chips M925HLU
Chipset: VIA P4M266A Northbridge, VT8235 Southbridge
Onboard Graphics: S3 ProSavage DDR Driver 6.14.10.25
Monitor: Samsung Syncmaster @ 800x600
DirectX: Version 9.0b
DVD Player: 4KUS DVD-16X5H Made by Liteon I think. (Have also tried another one (Pioneer) with same result.
Software: WinDVD 5, PowerDVD 4 (Both with same result)
DVD Region: 4

I tried reverting back to the ghost image I made of Windows XP with no software except PowerDVD installed and still got the same results. Interestingly, I captured a frame to post here as an example of the picture, but when pasting it into paint it appeared completely different. It was rather dark but the colors were fine. How does that work?!?
ANY suggestions appreciated at this stage! Thanks.

[Dash]

Update to my previous post.
I ran Norton Ghost to save my setup, then wiped the drive and reinstalled XP and the motherboard drivers (XP Original not SP1).
I then installed PowerDVD 4 and the DVD picture is perfect.
Following this I ran Windows Update and installed DirectX 9.0b and the driver updates for my motherboard. DVD picture still perfect.

Update 3rd May:
Best as I've been able to work out, if I install the video drivers before upgrading XP to SP1 all works fine, but if I install SP1 prior to the video drivers, I get the DVD picture problem.
Just one of those Windows gotchas I suppose...........