I recently got the error message concerning Windows defender and the message said to reboot or restart manually - I could not get the PC to start up, it freezes at that point - any suggestions?

Hello,

How far into windows do you get before it all freezes? If you can get past the welcome screen, and just as everything is loading do trl+alt+del. Look for something like windows defender or MSASCui.exe. then end the task, if that doesn't work, you could try using safe mode and uninstalling windows defender