This should help:
You can use the
Analytics clas, like follows.
Analytics a = new Analytics();
if(a.GpuCollection.Count > 0)
{
//...
}
Also you can query the collection and get more information about the GPUs, drivers and so on.
Hope this will helps you.
Reference:
http://forums.silverlight.net/forums/p/172663/389044.aspx