I am on Windows Vista.
The preference file is a file which contains a lot of info about the settings within ArchiCAD.
For me it is located at:
C:\Users\Laci\Application Data\Graphisoft\ArchiCAD 12.0.0 INT R1\ArchiCAD Basic.prf
Under XP and Mac it should be at some similar location.
If it is deleted, no problem, ArchiCAD will recreate it with default settings the next time it is started.
Maybe the file got damaged by some file system error or for some other reason. Not a big deal, the above will handle it for you.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac28