Upgrading graphics card?

Ok i have an Hp Pavilion 750n and it is pretty old but it can still run games like train simulator but when i run flight simulator things just start dragging, also i have the full version of fraps and whenever i start fraps it says.. "YOUR NVIDIA DRIVERS ARE OUT OF DATE!!! VIST NVIDIA.COM AND GET THE MOST RECENT DRIVERS" something like that. My video card is Nvidia Riva TNT2 64 32mb agp. I was looking online for a good graphics card that was 4x agp and 128mb and i found the Geforce Fx5200,now is this a good card? If i get this card will i be able to run it with only a 200 watt PSU? The minimum said 250 watt so will i have to upgrade my power supply or should it be ok? I am not an EXTREME gamer so i don't need more than 128mb video card. I just need a video card that will work a little better with my computer...if you can help i would appreciate it.