I’ve been here before. Hope everything works out.
If it matters, first thing I do is take everything out of all the slots that are non-essentials. Just 1 stick of RAM placed in the slot nearest to the CPU. The video card (PCI) I place in the Bus Mastering slot (first or second slot under AGP) and that's it. If you're trying the AGP card take all PCI cards out. Just the other day I was switching out CPU's and Memory. Two boxes same Mobos, I placed a slower CPU in the box and experienced the same symptoms you had, no communications to the monitor (even placed in a OS install disc). Right about this time I'm livid, so I put back in the faster CPU, all good. I move on to my other box and go to upgrade the RAM, it's my Libranet box so I have one stick of 128ddr in the first slot closest to the CPU. I put two other sticks in 256/512. Mofo wouldn’t light up either. So I placed them in this sequence 512-256-128 everything worked. I uploaded a picture of the sequence maybe it could shed some light. http://img213.exs.cx/img213/8120/420soyo18ot.jpg

But I have a few questions. Did you take your entire Ram out when you went to test his RAM, or did you leave them in and assume you'd get the info from the memory check or my computer properties? When you went to place everything back, did you place them in their previous slots or random? Check the videocard fan.

I believe I've read all that was posted, if I overlooked sorry. Good luck.