escape the target mode I tried to install Windows on my Mac Pro but it failed because my disk needed to be repaired; it was suggested that I hold cmd + r during a restart.

I tried that but when it restarted I was showed a grayish window that asked for my password. I typed my password but it won't work.

I retried several times but it refused my password. I am very sure I hadn't forgotten it because when I restarted normally it accepted my password.

Because I needed to install Windows so bad, I opted to transfer my data to another Mac, thus I was advised to restart my Mac in target mode. I did restart in target mode but when it started the grayish login window is presented.

Now since it won't accept my password, I basically have a dead computer and I don't know what to do. Any suggestions to get past this window?
From your description, I believe you're looking at the firmware password:



This isn't specific for Target Disk Mode, and would have been set through the Firmware Password Utility.

This script may be able to decrypt your firmware password, however it doesn't work on all Macs.

python -c "print ''.join(chr(int(c, 16) ^ 170) for c in '`sudo nvram security-password`'.split('%')[1:])"


Source: CNET