I have a compaq SR1630NX computer with a 300W PSU, I have installed extra ram so a total of 2.75 ram is in, a 9500GT is in and I have 2 dvd R/W drives and I have the Athlon64 venice processor. All working fine.
For you ... Power supply for your computer is 250W according to HP official website. I think you should be able to run the nvidia 9500GT in your system , as 9500GT's only require power coming from the PCI-E slot but do check what the 12V rail voltage is for your PSU. This is only if you are replacing the integrated graphics and doing nothing else really really heavy duty.