Unauthorized change to windows. Locked out of my computer! Help!

I recently installed Comodo Firewalll 3 and then it asked me to reboot my computer.

Now I get the message

“Unauthorized change to windows”, a problem with the validation and I’m locked out of my computer.

Please help. I am able to boot into safe mode but i’m unable to uninstall via programs. I get an error message when I try to uninstall.

Can you post the error message it gives?
And what version of 3.x do you have? current version is 4.1.x.920

Assuming you are on XP you can try the following. Push ctrl-atl-delete → this will start up Task Manager → File → New Task (Run) → explorer.exe → enter. Now see what happens.

In case Windows starts a browser try starting explorer.exe from within the browser by choosing File → Open and navigating to explorer.exe. Hopefully that should get you in Windows again. Once that is done we can troubleshoot further.