DVD playback not happening

Hey all A little help please
System specs
graphics card 7600 gt
2.00 gig Amd proc
1 gig ram
X-Fi extreme audio
2 x wd 80 gig drive in raid
1 250 wd drive
Generic DVD rom
Plextor 716a DVD writer
nforce 2 motherboard
All drivers are up to date
Speaker Logitec Z5500
I have checked PIO mode and made sure everything set to DMA if available
The problem is DVD playback is choppy and the sound is garbled almost like its playing too slow.
I never really bothered watching movies on my computer before just had a 17 inch crt. Yesterday I bought a Samsung 22" Syncmaster 225bw
I have tried PowerDVD 4.0 its old but It came with in bundle of some sort a long time ago. I tried my VLC player and Interactual player. I also downloaded the free trial version for Nvidia’s purvideo.
All work the same way choppy video and garbled sound. I have tried a couple movies retail copies of Transformers and Matrix Revolutions.
Is there any reason I cant play these movies,
I can try other movies but if I cant these movies I wont be happy with this set up.
thanks for any help!!

Just a wild guess -What resolution are you set 800x600, 1024X768??? Are you playing it on the dvd rom or dvdrw?? Also added did you update your power suppy to run all these drives? Also added uninstall the nvidia drivers and use microsoft drivers for the ide drives.

Well desktop resolution set @ 1680 x 1050, but it works fine playing games set there like WoW. Ill try it set lower to see what happens.
I never installed the ide drivers from nvidia.
right now I am ripping a non-protected video to see how that plays.
For some reason I can’t get my DVD rom to see a the DVD disk. So I am using my DVD -rw to play disks.
Ill see what happens after I finish ripping this disk.
my power supply should be good its a 430w antic p/s

I have checked PIO mode and made sure everything set to DMA if available

…which is not enough.

Which exact DMA mode is set???