Need help with upgrading graphics card.

[Butterkitty]

Ok so, I have a Intel(R) G45/G43 Express Chipset, and I want to upgrade the graphics.

Here's what I'm using:
HP Pavilion p6240f PC
Processor: Intel(r) Core(TM)2 Quad CPU Q8300 @ 2.50 GHz 2.50 GHz
Memory: 8GB
System Type: 64-bit operating system

My current graphics card is just not good enough to play the game I want. I don't usually game on my PC so I would just need something good enough.
Can anyone recommend one that might work with a 300W power supply or if it is even possible to add a new graphics card to this set up?
I would highly prefer if I didn't have to upgrade my power supply at all.

Thanks.

 

[toyota]

you will have to get a new power supply no matter what. even when brand new that power supply can only make about 160-170 watts max on the 12v line. after 3 years of use, it will probably be at least 20-25 watts less than that. so you are looking at maybe 135-140 watts available on the 12v where 90-95% of your power usage will come from. you could probably get by with a 7750 but your psu will be pushed to the very max during many games which will make it degrade even quicker. that cheap psu has no built in protection which means other components could be damaged when it fails.