I have an hp p6754y. It's got a quad core amd with integrated graphics. The power supply is 250w. I was wanting a little more as far as graphics goes, so I thought I'd try and pop my bros nvidia 9600gt in. Its got the six pin connector for more power.
Well, got it in there and plugged up. Powered on and it sounds like the pc comes on.. All the fans are spinning and you can hear hdd going. Only thing is nothing is displayed, the monitor never engages and also the blue led in the power button doesn't illuminate.
Ok, not enough power I think. I try a 300 watt psu, same thing. Ok, maybe still not enough.
I remove the card and try to start with default psu. It's doing the same thing. You can hear it start up but it's not booting.
I took the memory out and started up, no beeps.. What the heck happened???
Tried resetting BIOS after removing the card? Tried with the 300watt without the card just in case? Have you checked all the power connections? If they are all as they should be possible the motherboard gave up.
Move the jumper over with it of and then back before powering it up, another way is to remove the motherboard battery for a few moments. With all those PSU's and all connections right then most likely motherboard failed.
A graphics card is more likely to kill the PSU than the motherboard
looking at a review on Toms Hardware the nvidia 9600gt uses up to 200W (if that is all from the 12V PCI-X connector that equals about 17Amps)
[But it only uses full power when Windows has loaded and it is working hard]
If you have a multimeter use it to check the voltage from the 12V & 5V supply on a spare molex connector
If that is the power on the molex connector the the power supply or motherboard VRM is fried.
You should be reading 12v+- and 5v+- plus or minus 5% on the 5vline and plus or minus 10% on the 12v line. These are the maximun allowances.