os.system in a wxPython?

Hello, List.

I'm having the strangest problem. I'm designing what was meant to be a rapidly built little utility to automate a lot of 'setup' tasks that need to constantly be changed at work, the most important of these tasks being that I need to shuffle around some drive "Subst"itutions. Up to 4 or so at a time.

The GUI was designed entirely in the resource editor (...i looove this thing), then events mapped with eventManager to call my functions.

In them, I'm doing things like this:
  os.system(r"subst S D:\env\whatever")
And it takes at least 15seconds to execute. At least! But only if done from inside the UI. If it is done from a command prompt-- no problem. I tried a os.popen4 to see if it did any better-- just in case-- and it had the same behavior.

This may or may not be the right forum, but I have no idea what could be causing such an insane delay in what should be an instantaneous action. Any clues?

--Stephen