No, you can choose to disable the onboard card and install another one but it may, or may not be worth the effort/cost depending on the other hardware.

I had the same issue with G3 on a little 'puter I bought and it had the onboard video. While your specs might be showing 128meg of memmory, it is actually shared memmory with the rest of the computer rather than dedicated video memmory. Mine also was a bit short on the RAM and I suspect that is what's causing most of your issue. You'll either need to do some digging on your own or track down a slightly more computer savvy friend and see if you can't allocate more memmory to the video card and I doubled the RAM in that little computer (you really need at least 1Gb and a little more wouldn't hurt) which seemed to solve most of the problem. It still wouldn't run lots of background without issues but if you disable some of that stuff it should work with those mods.

RAM is pretty cheap and if those changes don't produce an acceptable performance, then you could try a newer/better video card if you want to and the extra RAM will most likely have been needed either way.

Oh this is assuming you're talking about a desktop computer, if it's a laptop you may be able to dedicate more memmory to the video card but changing it out or adding RAM isn't an option on a laptop...[]