The computer case size is a mid-sized ATX:
Height: 39.6 cm (15.6 inches)
Width: 18 cm (7.09 inches)
Length: 42.8 cm (16.85 inches)
I was thinking of upgrading the hard drive with a Samsung F4, upgrading the graphics card (but I'm not sure what would go in my PC, and the power supply (again I am not sure what will work in my system, but I have looked at the Corsair HX650W)
I was wondering what people thought, and whether they could give me some advice on what upgrades to make regarding the graphics card and power supply
If anyone requires more information, pleas say, and I will try to find it
I looked through all the documentation available for your unit but couldn't find anything on the PSU. So, assuming that you can't upgrade the PSU, the one caution I'll give you is that you'll have to limit your video card choice to one that doesn't require an additional power cable from the power supply, rather one that runs off the buss entirely.
It is a full width micro ATX system which opens up a lot of power supply options for you since it can take a standard sized unit. What do you do with your system primarily that is making you want to upgrade the graphics card and power supply? That determines what graphics you should be looking for which determines how much power you need.
If you are just using the built in GPU still then a graphics upgrade would definitely be helpful, and im always in favor of swapping out the POS power supplies that HP ships their units with, they are still passive PFC style units with the voltage switch which is an old design that really shouldnt be being sold these days.
with the graphics card il probably go nvidia, I just play games occasionally and the graphics card I have in is so loud, and struggles with some games, so i was just looking to get something more reliable