Cmd not working

You need to go into accessories then click on it for it to stay open.

sometimes a virus can take control of your administrative rights and will close down Microsofts system services on load. Try running MSCONFIG and see if the same action occurs. If so, you are likely a candidate for virus removal beyond the means of your current anti virus program.

Try renaming the cmd.exe as cmd.com in case of a virus hijack.
Should work, as some viruses often attacks to .exe files and they cant be opened.