The rename is the onscreen keyboard and copying the cmd exe. If you renamed cmd.exe you either found bad instructions or blew up your installed OS by not following the instructions.
-> YOU WROTE TWICE ABOUT RENAMING CMD. That's not what the articles I read advised.
So recently i forgot my password to the computer. So I installed Ubuntu and renamed CMD and Onscreen keyboard as each others. I went to the login screen, opened Onscreen keyboard and typed commands to unlock the computer. Now there's a problem. I can't rename CMD again because of trusted installer. And Ubuntu won't let me rename CMD. I can't use CMD properly. What do I do?