I have installed my new P35-DQ6. Would not start. I went back thought every component one more time.
FOUND MY ISSUE!!! Intermittent RAM module failing. Even the beep codes did not provide helping hand to isolating the fault. With both modules installed, sometimes the PC would start; often it would not even let me get as far as the BIOS. Eventually I got nothing, not even the monitor.
I removed all the RAM, and placed one stick into slot number one. PC would power up for 5 seconds, then power off, restart itself, run for 5 secs, then off again, and so on. I then removed that piece of RAM and inserted the second stick into the first slot. This time started up perfectly. Restarted the PC half dozen times without a hitch.
With both sticks inserted, the failing stick caused the PC to fail, not even getting far enough to allow access into the BIOS.
Team Xtreem 2GB KIT 1GBX2 DDR2 1066MHz CL5 PC2-8500
Will RA the Team Xtreem for something else. Not going there again. In concluding, I can not even be sure that the two earlier P35-DS3r boards I returned were the actual problem. Because the RAM fault was intermittent, it threw me of the scent of the real issue. I hope this helps anyone else experiencing similar problems.