Whats the specifications of your computer? Were you able to play games smoothly before you installed the sound card? Also what games are you trying to play.
My PC :
Intel Core 2 Duo 4600
MB ; GIGABYTE 945GCM-S2L
Soundcard Soundblaster X-Fi Titanium
Memory 2 GB
VGA NVidia GeForce 8600 GT
Speaker M50W Swan Hivi
What about power supply? Brand and model please. Your RAM is also going to be slowing you down, 2GB is nothing for Vista or Win 7, 4GB is recommended. The 8600GT is what is slowing you down. It's a low-end card. How much do you want to spend on a replacement? But first it's important we know the limits of your power supply.