Sometimes, my command prompt cannot find the PATH variable. I have this occasional problem at work where when I open command-prompt and run commands like ipconfig or subst, I get an error saying something like 'ipconfig' is not recognized as an internal or external command. When I try this echo %path%, it prints out %path% instead of the PATH value. If I look at my Environment Variables window, the PATH is defined right there but I don't know why CMD can't find it. At this point, I understand why the other commands were not being recognized since their paths are in PATH variable.

However, I cannot understand why the PATH variable is not being found. If I restart the computer, everything is back to normal. In a few days, I might have the same experience again.

I tried using this answer. It suggested changing a registry value but mine already had the value that was suggested yet it wasn't working. (The restart step at the end would have solved it as usual but that's not the point.)

Any suggestions regarding why the PATH variable may become invisible every now and then and how I can prevent it from happening again?