You can go head and put in the card I am almost certain it will run but your most likely going to run in to issues pretty quick HP have terrible power supply's you should just replace the PSU now instead of waiting for it to burn out or run in to other problems you don't want to make the room smell like burnt electronics if you know what I mean.
You will need to upgrade that PSU it will probably run fine for a little wile but sooner or later it will go out on you or random restarts so on and so forth. HP have terrible power supply's go for some thing like this http://www.newegg.com/Product/Product.aspx?Item=N82E16817153023 i am assuming it is a standard case this should work fine.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371034
This is a better buy.
Yes that is a much better power supply after rebate i was just thinking this would get the job done and its cheap but that antec is much better same price after rebate!! gota love newegg!
You can go head and put in the card I am almost certain it will run but your most likely going to run in to issues pretty quick HP have terrible power supply's you should just replace the PSU now instead of waiting for it to burn out or run in to other problems you don't want to make the room smell like burnt electronics if you know what I mean.