There is a problem with the Backups system when doing a full install.
When doing a full install, the installer simply overwrites the contents of the backups folders, instead of first checking for the existence of the backups folders, and if existing then creating new folders named backups1 , backups2 , ect.

The contents of both of these folders is overwritten:
C:\Users\<username>\AppData\Roaming\mIRC\backups
and
C:\Users\<username>\AppData\Roaming\mIRC\scripts\backups

I only learned of this problem today, when I upgraded from v7.55, to v7.61, and then to v7.63
I had downloaded 7.61 a couple of weeks back, but had not had time to install it till today.
Installing v7.61, I learned that it was already superseded by v7.63, so I downloaded that, and installed it.
It was only after launching 7.63 that the problem with the backups folders was apparent. All my settings from 7.55 had been wiped out. I checked for the backups folders, intending to restore my settings from those backups, and found the backups folders only contained the default .INIs for v7.61.