Msi Radeon Nvidia Geforce 8800 Gtx Driver Msi Radeon Nvidia Geforce 8800 Gtx I Decided To Buy NVIDIA GeForce7300GT (PCI Express) Could Some1 Plz Suggest Me Which Is The Best Card For Me?

I decided to buy nVIDIA GeForce7300GT (PCI Express) Could some1 plz suggest me which is the best Card for me? - msi radeon nvidia geforce 8800 gtx driver msi radeon nvidia geforce 8800 gtx

My CPU specifications:
Motherboard: Intel 915PBL
Processor: 3.0 GHz
RAM: 512 MB DDR2
and PCI Express graphics cards
I use MSI RX300-TD128E Radeon graphics cards, and now you want to edit. I decided to buy GeForce7300GT and NVIDIA, the NVIDIA GeForce 6200 and NVIDIA GeForce 6600, 6800 is in my head. which is the best card for my processor? Seller also asked me that I am the power supply in case of crossing my CPU to the graphics must be high to change, please inform me about the food because I do not know what it is. When I compare my MSI X300 all nVidia GeForce card, which corresponds to the same specification equequivalent for X300? I'm using Windows XP, these cards work with Windows Vista? Kindlly respond in detail and what they recommend is a map over the top? I buy a few kindlly Dayz quick to answer me. Thanks