|Your video card does not have a power socket on it. That would be a larger 6 or 8 "pin" socket, two rows of 3 or 4. |
That makes sense since your 9500GT video chipset requires only a 350 watt minimum or greater PS be on the system.
HP PAVILION A6742P DESKTOP PC support home page
"Integrated video is not available if a graphics card is installed"
That's the usual situation.
When you install a card in the PCI-E X16 slot, the bios automatically disables the onboard video, ignores the settings for the onboard video in the bios, and the ram is no longer shared with the onboard video. The computer user can't disable the onboard video in the bios by changing any setting.
(The only thing setting the Primary video or similar setting in thar case does is provide info that Windows needs - e.g. if you set that to PCI-E, a PCI-E card will be able to use it's enhanced capabilities in Windows via it's specific drivers having been installed - if that setting is set to onboard video or PCI, and the video card is PCI-E, the specific drivers loaded for the PCI-E card WILL NOT be able to the card's enhanced capabilities in Windows properly - you still get video in Windows but it can't work properly with that improper setting in the bios. )
"Power Supply: 250W"
Typically minimally sized on a brand name system.
It was a good idea of yours to upgrade the power supply, but how much did you pay for it and what make and model is it ? There are lots of el-cheapo power supplies that are a lot more likely to cause you problems.
So - your video card should work fine, unless the power supply is defective, or you damaged the power supply or the card.
The contacts on PCI-E cards / in PCI-E slots are very close together - if the card is even slightly mis-aligned, the card and the PCI-E slot circuits are easily damaged.
The PCI-E card must be all the way down in it's slot and it's end bracket that has the video port(s) on it fastened down, usually by means of a screw, BEFORE the computer is booted. Some PCI-E X16 slots also have a sliding plastic lock on the slot to lock down the inner end of the card. If it isn't fastened down, merely plugging in a monitor's cable when the computer is running can shift the card upwards in it's slot and damage it.
Your mboard should produce an error beep pattern if the card is all the way down in the slot and is defective or damaged, if there's nothing else wrong.
e.g. it's often two short beeps, a long beep.
I'm assuming, or course, that you have a case speaker hooked up or another sound device so you can hear mboard beeps, and you DO hear one short beep while booting when you use the onboard video.
If you don't hear any beeps, try the computer with the monitor connected to the onboard video when the graphics card is not installed.
If you STILL hear no beeps, your computer does NOT boot normally, then your PS has probably been damaged.
The warranty does not cover you damaging the card or the PS yourself.
If you need to replace the video card, you could do a lot better than one with a 9500GT video chipset, for not much difference in money. There are often many of them on sale, or that have a mail-in rebate, this time of year, and after Xmas.