Can someone please tell me if my system is compatible with this graphics card?

Solution
If you have a 450, the 650 should fit where the 450 is. Just make sure you have the power requirement. If you're worried about the power requirement, look at the 750s, they draw a LOT less power. They cost a little more, well, a bit more, but would fit your system nicely.
If you have a 450, the 650 should fit where the 450 is. Just make sure you have the power requirement. If you're worried about the power requirement, look at the 750s, they draw a LOT less power. They cost a little more, well, a bit more, but would fit your system nicely.
 
Solution