Computer speed decreasing after Graphics Card Installation

Hello Guys.
I'm a novice to computers and technology. So i've a question for all of you here.
I've a 2GB RAM and Intel Core2Duo Processor. Recently i installed a 1024MB Graphics card of Nvidia in my System. And What happend was, the performance of my system running WIN7 decreased..

I can't able to play music and video files and they stutter while playing..

Can anyone know why this problem is occuring?

Thanks in advance!

Source: http://broadbandforum.in/troubleshooting/69849-computer-speed-decreasing-after-graphics/

olga kurylenko harvard heat bulls usain bolt charles barkley weather atlanta tv guide listings