Age, also, alone, does not make a classic. I doubt
that the standard
run-of-the-mill '386 PeeCee will ever amount to anything except to,
perhaps, archaeologists who dig one out of a landfill. There were too
many of them made, and they were (are) regarded as "disposable". Look
at the construction - modern machines aren't made to be repaired any
more than a disposable cigarette lighter is made to be refilled. They
burn out, you toss' em, and buy another one.
Well, not quite. You'll have a motherboard problem with Packard Bell, Compaq
and the like -- but many use "generic" motherboards; thus a Baby AT case
would fit anything from a 286 to a Pentium whatever (btw, shouldn't a P5 be
called a Pentium Pro Lite?)
Floppy disks, of course, have been standardized since the original PC, both
in interface and form factor; EIDE/SCSI for hard disks, IDE for CD-ROM's.
I upgrade PC's much of the time (probably sell 10 used systems/upgrades to 1
new system) and can tell you that upgrading _is_ viable in the PC world.