how to reset a lost admin password?
Solution 1:
"Boot up the machine,and after the BIOS screen, hold down the left Shift key." Did indeed NOT log you into the machine. That is correct. You are seeing a menu instead. If not, then don't read any further and try again.
If you do see the menu: Choose "Advanced options", then choose (recovery) from the menu. Then you see a lot of text passing upward on the screen. Do nothing. Then you see a colored menu. Choose "root".
Type:
mount -o remount,rw /
passwd your_username_here
change your password
then type:
reboot