Powered off today before going to work.
P.o.S P3 now fails to start up, gets into the pre-load screen and freezes, with lots of disk activity but no indication that anything is working.
(30 minutes later after much reconfiguring of hardware)
And in a fit of extra speshul short bus behavior, (1) it doesn't recognize my keyboard when plugged into the keyboard port but DOES in the USB port, and (2) extra extra speshul micro-wonder-soft-ful, it thinks the borked up state that I have been seeing is the last known good configuration. Because all good configurations DON'T present the user with a working GUI.
(and 20 minutes later)
OK, finally got rid of the stupid SP3 plague. System came up in user account again which I can fix ... but at least I have no reason to want to throw explosives at things.
I _may_ still go ahead and put Linux on this thing, for grins.