When I try to open a Command Prompt in Windows 7, the following message comes up:
Windows cannot find 'cmd'. Make sure you typed the name correctly, and then try again.
How can I overcome this problem?
Have you checked for/cleaned some malware recently? Sometimes malware will hijack the cmd.exe and cleaning the infection can render the cmd.exe missing/useless.
Have you tried Windows 7's in-built System Restore to restore to a point when it did work? If not perhaps you could try that.
Perhaps run Window's System File Checker to see if it can find/replace the missing cmd.exe (if it is indeed missing).
I had the same issue, solved by running Malwarebytes.
Go here install/update and run a full scan.