When you type SET or PATH at a command prompt, you notice that the %SystemRoot% environment variable has not been expanded. To correct this problem, edit:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment\Path and make sure that Path is a type REG_EXPAND_SZ.
If it is not, double click on Path and press Ctrl / C to copy the string to the clipboard. Delete the Path value and re-add it using Add Value. Set the type to REG_EXPAND_SZ. Paste the string by pressing Ctrl / V. Now edit:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRoot and make sure that this REG_SZ value conains the proper path (C:\WinNT).