You should find the latest drivers on the official sis site:
http://w3.sis.com/download/
where - i think - you'll want to make this choice (possibly the x64 XP version):

which results in this info, at least suggesting that a more recent driver is available:

please think about the driver you download


NB: good to know - I only really ever play on ender's client (recently, my own) so I have little experience with the default client. I'll try and remember that OpenGL 1.5 is required