I would check the size and power requirements of any video cards you consider upgrading, though (assuming you try that). HP tends to use small, cramped cases which can resist upgrading (not to mention air flow and heat problems once you get past the physical restrictions), and use small sized, low wattage power supplies inadequate for running much more than the original configuration.
Considering most of the better graphics cards have a fan built right on them extra cooling is not an issue.I have not seen a pc yet that could not be upgraded yet do to cramping.And a 300 watt power supply is pretty sufficent for any rig.
