I've tried set path=c:\blah\blah;%PATH% with and without the appended PATH part. All within ...\system32\AUTOEXEC.NT Rebooted each time. No joy.
The PATH on my old XP has lots of items starting with the defaults and ending with the item from the AUTOEXEC.NT file.
The new XP's PATH only contains
c:\WINDOWS\System32;c:\WINDOWS;c:\WINDOWS\System32\Wbem
no matter how hard I try to change it. Could XP be copying the default from the repair partition / folder???