I don't think this will fix his problem, I don't think he would of even tried to edited this folder in anyway before his problem occured.
Before messing around like this just try typing in ipconfig/all
this may resolve your problem
if his system doesn't like ipconfig, says it's not recognised as a command then how will adding a switch to the unrecognised command help?
ipconfig runs the ipconfig executable (located c:\windows\system32\ipconfig.exe)
ipconfig /all runs the same executable but with a switch...
ipconfig = not found
ipconfig /all = not found but with an added switch...
if the system can't find the executable then surely the best approach is to check that the file is actually there, and not deleted.
then if it is there check that your system variables (PATH in this case) is set correctly so it can find it.
I suggest that you try to replicate this problem. I can only think of two ways to do this, move or remove the ipconfig executable or type path=c:\windows at the command prompt to cripple the system variable.
both of these will replicate the problem.
assuming that ipconfig /all will magically make the program accessible why not try some more switches there are 9 to choose from. but all require the ipconfig.exe file to be available to start with!