You know the measurements for the video card, then you can open the PC and measure the area intended for card. It's really that simple. The HP system is typical desktop type case. Unless is a known obstruction it will work within your measured checking or not.
the 6870 is 10.3 inches long according to newegg. so my question is whether that will fit into my computer or not...here is a link to my comp specifications, the info on the case is near the bottom.HP Pavilion p6720f Desktop PC Product Specifications HP Pavilion p6720f Desktop PC - HP Customer Care (United States - English)will it fit?