Just wondering... do you have "non-administrative" accounts, as well (not including the "guest" account")...?
From what you have described above, it doesn't sound like either a hardware problem or an "OS problem".
Rather, it sounds like something wrong WITHIN your existing administrative user account.
This is why the "guest" account may still work ok.
What happens if you try this?
- Power down, all the way off
- Press AND HOLD the power on button. DO NOT LET GO!
- Keep holding it in for about 6 seconds and let go. If you see the screen display "loading startup options", you can let go a second or two sooner.
- You should in time see a screen showing you the internal drive (left) and another icon named "Options" on the right
- Click the "options" button, then click "continue".
- Let the recovery options load.
If you can get this far, then you know
- The hardware is probably ok
and
- The OS (at least the recovery copy) is ok.
What you could try here (a real "backdoor trick"):
Use terminal to delete the file
/var/db/.AppleSetupDone
WHY you want to do this:
The ".AppleSetupDone" file (which is invisible because of the "period" in the name) is created the very first time you set up the Mac with a user account. After it has been created, the Setup Assistant won't run again.
BUT... if you delete this file and reboot, it will [once again] open the Setup Assistant at boot.
WHAT TO DO NEXT:
It will "look like" the Mac is "brand-new", inviting you to create a new user account.
YES, you want to do this.
Doing so WILL NOT DELETE the existing user accounts -- it will only create a NEW one, "empty and clean".
Give this user account a special name and password (not the same as your "regular" user account).
It will exist "for test and recovery purposes" only.
You can delete it later when things are up-and-running again.
Once you have the new account (which will be an "administrative" account by default), now you can see if you can use the Mac normally -- that is, log in, get to the finder, open files, run apps, etc.
At this point, if the new account behaves "normally", as it should, now you have a working Mac again and from this point start working on "what went wrong" with the existing administrative account.
I -think- this is the proper "full" command in terminal to delete the AppleSetupDone file:
rm -i "/Volumes/Macintosh HD - Data/private/var/db/.AppleSetupDone"
(the quotation marks are included and part of the command)
If you have renamed the drive, you need to replace "Macintosh HD" with the new name.
WARNING WARNING
I'm not sure if the full command is correct.
I believe it is, but my "terminal fu" is not strong and I welcome correction from others.
Good luck.
