HELP...this is the weirdest thing...

Ok so here it goes. I am fixing a Sony Vaio for a friend. When I get it, it powers up, but then nothing...no picture, no beep codes, nothing...except you can hear the hard drive and fans running. So after resetting the cmos and changing out all drives one by one, I suspect a motherboard problem. So I order a new motherboard and CPU. When I get it in, I put it in a new universal case, with all of her drives. Same thing happens...blank screen. So now I have replaced the motherboard, cpu, power supply and hard drives (new computer pretty much) and nothing...You can hear the hard drive boot up, but no picture (even tried new monitor). Any ideas out there?

You didn't mention a video adapter?

since you mentioned a "case" I assume it's a desktop Vaio...

I am familiar with a problem with the exact same symptoms on the "S" series laptops...and Sony even recognizes the problem but has never issued a recall on the motherboards... either at boot or when the system tries to wake from hibernation the video fails to initiate

Is is a desktop and we replaced the motherboard...it is basically a brand new computer built from scratch with the same problem...

check the power supply make sure it is sending the amount of energy its supposed to.. this is happen to me before.. if that doesn't work.. disconnect any fans that you have in the system and than see what you can get.