The Power Supply more than likely but check the number of Power Connectors that you actually need and include the Video Card in this as it takes power directly from the PS. The size is the important thing here as a Standard PS is one size and quite a few HP Dedicated Power Supplies are different and not a Standard Size. Compare your old one size and external plug Sockets the way that the mount on the Power Supply some HP PS's have the plugs internally to allow a smooth surface to slide against the Case. If at all concerned look at the Antec Power Supplies as these have a 20/24 ATX plug that involves dropping off the last 4 pins if you need a 20 Pin PS and if the ATX plug is separated you just have to clip back in the 4 pin plug to make it a 24 Pin Plug. Antec PS have a Constant Power Rating as apposed to a Peek Power Rating so if you look at a 400 W Antec it can produce 400 W all day every day where as other brands can produce a Peek Load of 400 W but will run normally at much less.
As for the Video card it will fit but needs to be placed in the correct PCI Express Slot for best performance. Just remember if you are not using Vista Direct X 10 isn't an issue as only Vista currently runs it.
If you are using Vista you need to remember that Vista is a [b]Major Resource Hog[/b] and you'll need a lot of Video RAM and System RAM if you want to run games at the optimum speed. Frame Rates on Vista are much slower than they are on XP with the same Hardware/Software combination.
A base install of System RAM for XP should be 1 GIG and for Vista 2 GIG's or more depending on what the M'Board can support. While both OS's will run on less they just work better with that size RAM as a starting point.
Col
