The upgrades bit is just pointing out that the computers you listed are not really anything but faceless things. They were premade and sold as is, you could spend lots of dollars and maybe upgrade them, or you buy the new more advanced version. Unlike today's computers sold off the shelf, you can put what ever you want in them after that. They might start all the same.but they aren't locked that way. Unless you buy a Mac...but that is another story
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And yeah Windows hasn't really changed that much, but there are some nice changes that make it a lot more user friendly to me. I really love pinning my most used programs to the taskbar. And I can agree that software isn't always using everything PCs could give it, but it is (to me at least) caused by programmers trying to make sure their programs work on weaker PCs so they can get a larger market. And being lazy.