This is one of multiple  reports about problems with finding and reading HOME/.idlerc/*.*.  I believe that if nothing else, Idle should issue a warning message (that not not crash Idle), set a flag, and continue. The configuration dialog should also warn that changes will not be saved.

This particular situation is about a Windows system with HOME set but pointing to a directory on a drive that is not currently mounted.  The user could create a .bat file that resets HOME, but Idle could also try harder to find a usable directory (so that the installed version specific icons work).  Currently USERPROFILE is used (in os.expanduser) as a backup if HOME does not exist.  It could also be used as a backup is HOME exists buts is not usable.  Dittle for HOMEDRIVE and HOMEPATH used to backup USERPROFILE.  Or Idle could change 'x:somepath', where x is not 'c', to 'c:somepath'.

Or maybe Idle should recognize an IDLE_RC env var so a user like Cemal can run idle with the same set of user config files regardless of whether connected to a corporate network or not.  This would also help someone (like me) who wants to use the same config files regardless of whether logged in and running as admin or normal user.