You can't do it with this level of preciseness in the Mac family at least. Between OS X, probably as long as you're not on non-intel processors.

Like other commenter said, Windows/MS really goes all the way for backwards compatibility.

You can take a G3 from Mac OS 7.1.2 (version which added PowerPC support) all the way to 10.4, which would take you from 1997 to 2005. I haven't done it, but I've read that getting 10.4 requires some finagling to achieve, so the last supported install you could do would be 10.3.9

IIRC the minimum OS for a G3 was actually 8.something. (Apple generally doesn't/didn't support down-level OSes on their hardware.)

Also the settings would have only been preserved in Classic, but that's to be expected I guess.

Wonder if you could upgrade them, and then just rip out the hard drive and move it to another box. Wondering if 10.4 would be ok with one moment having a PPC and another moment having an intel processor.

If at OS X you take your previous computer and attach it in target disk mode or something (I'm not a Mac person) will it do anything with the old OS, perhaps use settings or allow apps to run under emulation or such.

Such quirks are partly what would make such things interesting.

Slackware goes back to 1993, is there an earlier Linux distro still in major use? (looks like there isn't - http://upload.wikimedia.org/wikipedia/commons/8/8c/Gldt.svg).

It might be more interesting with Linux to follow a WM?

You can do that with most unixes easily.

In Ubuntu, it would be one long series of do-release-upgrade commands. Not nearly as exciting.

Not in itself. The interesting bit would be playing with different UI's and testing backwards compatibility of settings and apps. Such as the OP video does between upgrades.

I wouldn't mind seeing the same video idea with Ubuntu. Somehow I don't think it will be long before a copycat does this :)