What do I need to make my PC better for gaming?

You got more than enough RAM.

For the graphics card, it shouldn't overheat, but if it can handle the newer card, depends on your Power Supply Unit (aka PSU).

Could you post it's full specifications (not just total wattage), or maybe it's model?

CPU and RAM look good. I have to ask though, is it DDR2 or DDR3? I don't remember any mobos with C2Q and DDR3, but it's better to clarify. While we're at it, motherboard make and model?

Also, please list make and model of the PSU, like it was suggested by Sunius.

Your graphics card appears to be the weakest spot right here. Everything else looks quite good. What kind of case do you have? That will decide on the overheating possibility. If it's a cheap crappy case, cooling isn't so good, so you will have to upgrade in order to get a better card. Case upgrade is worth it, though, a good case can easily last you through multiple builds.

Oops, forgot to say 8192MB RAM

The model is HP Pavilion p6267c: http://h20000.www2.hp.com/bizsupport/TechSupport/Docume...

DDR2. It's an Asus, here's a full list of all the specs: http://h20000.www2.hp.com/bizsupport/TechSupport/Docume...

I'm worried that my computer won't be able to handle a new graphics card, the case is the one that came with the computer. "Mid-size ATX"

Also, I have no idea what PSU this has, I know it's 300 watts but that's about it. Do I have to take my computer apart to figure that out?

You can just open up the side panel and read the label on the PSU...that shouldn't be too much work even with an HP case. I use to have the same case...there is a thumb screw in the back and the side pannel slides strait back and off.

I'm definitly no expert, but even for the lower or mid-range cards you usually need more of a power supply.
When I upgraded to a Geforce9800gt (which is a pretty cheap card), I needed a new PSU.

also, being that you have a factory case...make sure that the video card will actually fit in your case

I'd get a i5 3570. Get the k series only if your gona overclock. 8GB ram will be enough. A GTX 650 ti or a GTX 650 ti will be good.
For games it all depends on the CPU,GPU and the ram.

Oh and also a 1TB hardrive will be good

I meant GTX 650 ti or GTX 660 ti

300w isn't enough, you'll need a 450w but I'm no expert

You can "get away" with a 7750 on 300w but I highly recommend upgrading the PSU.