Thank you for the discussion but I don’t think we have the real solution for the moment.

And yes, my install procedure is:

  1. Install Clean Windows XP SP2
  2. Install Avast!
  3. Try run command.com, and it failed.
  4. after remove that line from config.nt, command.com work again.

Another case is:

  1. Install Clean Windows XP SP1
  2. Install Avast!
  3. Try run command.com, and it work!

And in the above case I haven’t install any Symantec/Norton related software.

If it is to edit the registry to solve the problem, I think it is not a good solution as I think WinXP SP2 already released and more and more people will use it.

Is it a problem of SP2 or Avast! now?