This G3 iMac uses onboard ATI video, but the 16 MB of video RAM it has is not shared with the main system RAM. Actually I should say that it has a separate video RAM module, but I guess some sharing could still be going on.
I was mistaken earlier when I said I had NT 4.0 on that machine. I believe it was Windows 2000. The computer I had before my current Dell was a 1.6 GHz Dell small form factor Dimension, and I believe I had XP on it, but it was not fast. It had 2 GB of RAM, and that's all it could handle, which is why I upgraded to our current Dell Dimension (E521). I have 4 GB of RAM in it and it runs fairly well. It came with XP, with a free upgrade to Vista. I did that, and after a few years, took Vista back off and re-installed from the OEM XP disc. That was a few years ago, and it's taken to be a little sluggish again, so I'm up against another reformat I think.
This is what got me thinking about switching. XP is not really supported anymore. IE9 is now Vista/7 only, and I suspect we'll see more of that as we go forward. The screen is a 4:3 19" Dell screen which is okay, but not superb. I'll want/need to upgrade to 7 on it, but I'm just not all that excited to do so. I figured I could spend a few hundred bucks on a snazzy new monitor, a hundred bucks or more on Windows 7 upgrade(s), and in the end, I've still got a system with a large desk footprint and cords everywhere. I could go to an All-In-One Windows PC, but they're close to a grand already. With the stunning Apple displays, the more eye-pleasing-to-me case design, and just a few hundred dollars more for a long-term investment, that's the way we're going to go.
To be sure, it's not for everyone. My brother switched a few years ago, which is what really got me interested. My dad (hardcore Windows user) says he'll still speak to me after the switch.