I 've been using a P35-DS3R mother board in RAID1 disk configuration for some time without any problem :

After seven months the MB began to fail at boot time.
There is what looks like a power failure one second after powering the PC, then the PC hangs some few seconds and restart again (and so on...).

I thought it was a power supply fault and changed it (with a bigger one). Unfortunately I still had the power failure at boot time.
Then I tried to unplug the hard drives one after another and found that one of them was faulty (or looked like faulty because the PC was OK when I disconnected it), so I sent the HD to my provider and had it replaced.

Yesterday I received a new one and had it connected to the computer, and ... once again the same failure at Power Up when the two HD are both connected to the PC. (The two HD are WD 2500AAKS -250GB SATA II).
As the HD that was sent back to me has not the same serial number I suppose this is not the very same HD that they sent back to me and besides it was delivered in an antistatic sealed package as a new one, so here is my question :
Is it possibly a fault of the MB that could produce such a power failure at Start Up ? Is there any test I could perform to decide witch part is faulty ?
Thank in advance for any help.