Eg : intel r(r) g33 /g31 express chipset family update drivers 32 bit update

I won't be able to play .mkv movies on my PC. I have lost the original driver cd which I got along with the motherboard. I formatted my PC few days back so I downloaded the drivers from some site, which in turn are not allowing me to view the movie's with .mkv or .mp4 extensions. Only .avi formats are supported by my system. Prior to formatting, I was able to play any format. Please help me by suggesting a proper graphic driver. I am having Intel(R) G33/ G31 Express Chips Family. Thanks Avinash