subprocess problem on WinXP

[Wolfgang]

Hi,

I want to compress all files (also in subfolder). The code is working 
more or less, but I get a black popup window (command line window) for 
every file to compress. How do I cave to change my system call that 
nothing pops up?

Wolfgang

import os
import subprocess

dir="g:\\messtech"

for root, dirs, files in os.walk(dir):
     for file in files:
         f=os.path.join(root,file)
         subprocess.Popen([r"bzip2",'', f],shell=False).wait()