general question
 

I don't have any PentiumD 9**. Does this processor have four CPUs, two of them virtual HT ones?

[QUOTE=paulunderwood;120244]I don't have any PentiumD 9**. Does this processor have four CPUs, two of them virtual HT ones?[/QUOTE]There is no HT in the PentiumD's. Standard dual core, single thread per core.

[quote=paulunderwood;120240]Have you tried running the memory at 333MHz i.e "x 1.66" of 200MHz ?[/quote]

Yes, and I have also tried slackening the timings, and I still had errors.

Can you try running small FFT and large FFT torture tests? If it's failing on small FFT, then it's the CPU. If it fails on large FFT, then it's the memory.

To isolate a memory problem, I would try running:
1. memory at CAS3.
2. run memory at reduced speed and CAS3
3. run memory at reduced speed, CAS3 and bump voltage up 0.1V

What about double the RAM bandwidth with another DDRAM if you have access to some ?

Upgrade your chipsett driver ?

just to give some idea.