Windows XP to Win 10 migration issue

I have a database in Windows XP (old PC), postgresql 8.4.5 which needs
to be migrated to Windows 10 Pro (new PC).

Now, for the bad news, the XP PC, when I powered down, before doing any
backup or database unload, would not power back up.  I will be
attempting to get the PC fixed for that.  In the meantime, I removed the
old PC HD, installing in a SATA to USB box and I installed the same
version of Postgresql (8.4.5) on the Win 10 machine, thinking I could
simply copy the data folder from the XP's HD to the Win 10's HD into the
appropriate folder (C:/.../8.4.5/).  I did the copy of the data folder,
after renaming the new, unused data folder to preserve it).  I stopped
the postgres service, made the copy, and attempted to restart the
postgres service.  No Go!  Would not start.  As a double-check, I
renamed the copied data folder to something else and renamed the
preserved data folder back to it's original name, and the service
restarted just fine.

So, without being able to backup or unload (dump?) the original database
on the original PC, what would be the best way to move data to the new
PC?  Or, IS there any way to do this, without reviving the old XP, PC?

Dale