P6310y HP PC Computer upgrade to radeon card?

First off. Specs:
AMD Athlon II X4 Quad-Core Processor
NVIDIA GeForce 9100 Graphics
1 Terabyte Hard Drive
6 GB DDR3 System Memory

Secondly I should state I'm 14 years old and have very little knowledge of computers past the internet and things on the computer.

Ok so what I want to do is upgrade my graphics card to a radeon due to my computer constantly overheating due to my graphics card struggling to run minecraft and other cpu intensive games.

What I would like to know how to upgrade my power supply in the computer and if the case is big enough to support a radeon graphics card, or what graphics cards would work with it that would be good for gaming.

Yes i know this isn't a gaming computer in the slightest. Thank you for taking your time to read my question.

Guest

We need to know what pc case you have mid tower, full tower { which is good for cooling effects and plently of room} just looking at some of your specs could go with a gtx 650 ti or a gtx 660 with a good brand 600 watt psu, i'm guessing you have atx psu, there only four screws holding it on the pc back plate and pulling out the connectors

starpc11