Hello

Something has happened to my mac

if I try and boot it just sits there forever

If I try and enter recovery it just shuts down.

What can I do?

Have you got an OSX disk? You should try booting from that or trying an internet recovery.

If you cannot get it to start try removing each stick of memory whilst powered off and then power-on without each stick one at a time in case the RAM has gone bad.

Boot into the Mac with CONTROL + S

In the black and white command line screen that appears, type: mount -uw /
Then press enter
Now type: rm /var/db/.AppleSetupDone which will remove the file telling the mac it has been configured.
Nor press Control + D and it will reboot and you will select language and locale etc. and configure a new user.
You can now change the other user or delete it as you wish.

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