The installer was changed for a newer and more up-to-date look and feel. Yes, it could be combersome to help users upgrade, but in the future should be more helpful. You may try a batch file, and have the user run it to make it more 'automated'.

Code:
rem mIRC Backup/Restore Script
rem 
rem Based on the presence of a backup folder, this will backup
rem or resotre mIRC settings files.

SET backupdir=mircbackup
IF EXIST %backupdir% GOTO restore

:backup
IF NOT EXIST mircbackup MKDIR %backupdir%
IF NOT EXIST mirc.ini GOTO noini
FOR %%f IN (*.ini) DO COPY /Y %%f %backupdir%\%%f
ECHO Backup created to %CD%\%backupdir%
GOTO exit
:noini
ECHO Could not find mirc.ini--backup could not be created.
GOTO exit

:restore
IF NOT EXIST %backupdir%\mirc.ini GOTO nobackup
CD %backupdir%
FOR %%f IN (*.ini) DO COPY /Y %%f ..\%%f
ECHO Restore completed successfuly.
GOTO exit
:nobackup
ECHO No backup was found. Please create one before restoring.
GOTO exit

:exit
pause