The stock power supply is only 250 Watts so that's a far cry from the test setup noted at:
The connector on the back was indeed power and this is not a good choice for this old box.
Try the usual under 30 buck ATI 5450 1GB card next.
Just recently picked up a Compaq SR1910NX. Its an old PC with an integrated graphics card. I just needed it to view YouTube videos and write the occasional paper on MS Word. Long story short, I can barely view YouTube videos (fullscreen is WORSE) because of the shared memory between the pc and graphics card (and It came with 1.43gb installed) Ugh..anyway I went on CL and bought a used NVIDIA GeForce 7900GS PCI-E card. I've never installed a PCI-E express card, just PCI. It has a connector on the back on the card, im guessing to hook to the power supply but im stumped as to how. I plugged it in without a power supply and the fan came on. *shrugs* idk..i have a lot of spare connectors in the pc from the previous owner but none look like the connection on the video card. I need a little help. If needed I could snap a couple picks.