I noticed that the date of the currenlty installed Linux kernel Revision/Version is later than the System's install date.
2.6.32-25-generic# uname -r
These figures seem to answer my own question, but what surprises me is that I don't remember a dramatic "You must reboot Windows now!" dialog, which I've grown to expect for such a deep system change...
Maybe I just clicked OK ..Windows style :)
Is the kernel somehow able to "replace" itself? ... or maybe it can only do "minor surgery"?
eg. Could I still be running "Lucid" in 2020 with each "latest" kernel being installed via updates. (I'm not going to do that; it's just a test scenario.)