***SOLVED***
Problem with installing TC (from USB to HD) was the whole time the HD was kept 'busy'. At the end the installation could proceed once I used the command "sudo fuser -km /dev/sda1".
This is obviously forceful way to dismount the HD.
Persistence pays off at the end. I am amazed about the startup speed on this old laptop (Dell Latitude D510). I like this minimalistic approach. Lets explore the possibilities :-)
...and of course thanks all for helping out. I am a layman in this area.
...and the WiFi works also (I suppose it has to do me not checking all 3 boxes last time).