My Steelseries World of Warcraft MMO Gaming Mouse: Legendary Edition doesn't work right

[Huffulumpagus]

I got it secondhand, and While two of the thumb buttons do work, the other two and the pinky button do not. I'm assuming this is because I don't have the proper drivers for it, but on the store page on the Steelseries website I couldn't find a download link for them. Does anybody have a link for the drivers or just a guide on how to fix it?

 

[penguintech]

http://steelseries.com/downloads
close to the bottom of the page under legacy device software