When I de-install AC7 I find the prefs in the root of the ArchiCAD folder, with 7.0 in the name instead of 8.1.
When I rename them to 8.1 and put them into the prefs-location you mentioned and overwrite them nothing happens.
You
are
on a PC? [not in your signature]
Now I am NO computer science whiz, but I believe that the two versions are basically separate and different "animals", so overwriting from one version to another is not an option. So as I said before you will have to go through the task of setting up your preferences in ver 8.1, either rebuild/update,
from scratch
. Then you will have them available to you. There are a couple of other pref files kept in the same folder, Plotmaker prefs etc. and I just drag a copy of ALL of them when needed and on my next start up I'm "good to go".
jeff white
w3d design
AC 23 Solo US / current build & library
Windoze 10 Pro 64
HP ZBook 17 G4
Intel Zeon 3.0
Twin 2GB SSD
32 GB memory
http://w3d-design.com