Just delete them.
If you don't have 14 on your machine it won't do any harm - you are going to re-install it anyway.
It is really just the program folder you need to delete as Archicad won't install into a folder that already exists.
It will replace all the other bits if you don't delete them.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10