Have you lost your path variable? It happens… While working in windows, this can happen.
I was lucky, I found it in HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\Session Manager\Environment
If you are a developer and modify your path from time to time, it is best to have a backup… Actually, backup even the registry… but in a emergency… this will work fine At least it did for me. I found the answer in another site… Note that the path is user + system path combined.