according to : http://www.findlaptopdriver.com/3646h-hewlett-packard-mainbaord-specifications/
you have a PCIE x16 (no revision mentioned) but I would assume by the type of mother chipset it should be at least 2.0.
can it run a GTX760,, not likely as you will need a LOW profile video card on your system to fit in the case of that HP.
basically; he problem is the 240 watt PSU and the need for a single slot, low profile card in that computer
so no to GTX 760.