As it is now; when I end up reinstalling my OS, I'll be installing mIRC v6.21 first and then v6.3 just so I'll have everything where I want it
Why bother with all that when you can just create an empty mirc.ini file in the intended install directory?
There shouldn't be any major issues with navigating to the mIRC folder. The download/log folders are both accessible via the Tools menu. Power users should know enough to type
//run $mircdir or use the command line/mirc.ini methods to restore the old behaviour.