Enable Command Promt Disabled by Administrator or Virus

1) Click on Start and go to Run. Users of Windows 8.1, Windows 8, Windows 7 and Windows Vista, go to Search. 
2) Copy and paste the following command and execute it.

REG add HKCU\Software\Policies\Microsoft\Windows\System /v DisableCMD /t REG_DWORD /d 0 /f

3) This should enable the command prompt. If it is still not enabled, restart your computer.