DVD Playback problems. Slows down

Ok first comp specs:

Windows 2000 Professional Service Pack 4 (build 2195)
1.10 gigahertz AMD Duron
128 kilobyte primary memory cache
64 kilobyte secondary memory cache
Bus Clock: 66 megahertz
236.54 Gigabytes Hard Drive Free Space
256 Megabytes Installed Memory
BENQ DVD DUAL DW1610 [CD-ROM drive]
PIONEER DVD-RW DVR-108 [CD-ROM drive]
NVIDIA GeForce2 MX 200 [Display adapter]

InterVideo Inc. - WinDVD Application Version 5.2
Directx9
QuickTime QuickTime 6.5.2

There are no other programs running in the backround.

At times I can run 5 minutes worth of video and it works fine. Other times I get 5-15 seconds. The video will play fine at first and eventually sound will go out and then I get the herky jerky until it grinds to a halt.

I figure this is a memory problem. I set every acceleration issue I could to maximum performance from quality. I changed pagefile to a gig. I used the nvidia manager to go for performance. I can see the effect of all of the performance options with some streakiness of video quality but dvd's still grind to a halt.

Is there anything else I can do to get dvd's to work on this computer? Will upgraded ram to 512 make a difference or is this computer just too old ?

Thanks

 

Addendum: Fresh install with format C and dvd's tested before and after each software/firmware update.