Okay - I've sussed out that they are "Cabinet" files and store information in a compressed form differently from the way ZIP files do.
I have full "Disc Image" backups (Acronis True Image) of my hard drive partitions which can restore EVERYTHING exactly as it was at the time the image was created.
There are over 1,000 CAB files on my hard drive, all of which take up space.
If I have understood correctly what I have read on the net, the main purpose of CAB files is to store info used to set-up programmes initially.

My questions are :-

Once my system is set up and programmes installed, do these CAB files then serve any purpose, or do they just take up space?

I have them saved in backup copies of my hard drive (so I can put back, in the same location, anything I remove), so can I just delete them from the working drive?

Your thoughts are appreciated.

Quack!
Geoff the Duck.