1) If you have X-Windows (the graphical interface) working at all, then you have a graphics driver loaded - that's what gives you graphics in the first place. Are you asking about the "Compiz" stuff that appears under Preferences - Appearance, the Visual Effects tab? That is not going to work on all hardware, especially old hardware, since it requires 3D graphics support in hardware. It's a luxury, not a requirement, and on a slow laptop you're probably better off without it.
2) That driver you downloaded - is that in a TGZ file rather than TDZ? If so, that's like a ZIP file: just a container for files. Extract the whole thing to a directory have a look inside for instructions, such as a README or INSTALL file. You'd probably need run scripts on the command line as root, which you'd use the
sudo command for.
But is it definitely a
current 3D driver for
that hardware? I don't know that chipset specifically, and I'm struggling to find any details on it, even from
SiS themselves. (There was a SiS 340, but no 430). X-Windows has undergone some major changes over the last couple of years, and there's a real risk that X-Windows could just stop working if it's not the right driver, or too old. (Linux is not as friendly as Windows in that area.) If that was my system, I would want to know that installing a new graphics driver would make a real difference, before I risked it.