My understanding was that subprocess.py was supposed to be 
backwards compatible with at least Python 2.3 if not 2.2. Wanting 
subprocess and backwards compatibility, I grabbed the subprocess.py 
from 2.4b1, changed the import if so that win32api was used (since I 
had no _subprocess library!) and found several problems, of which 
this is is the mildes:

when using subprocess.Popen on Windows I get one or more windows 
called C:\WINNT\system32\CMD.EXE popping up. Sometimes they 
stick around, other times they are only around for a short time. Note 
that I don't see this probem using os.popen3 (on the 
other hand, os.popen3 has inferior error handling).

The following code is one example:
from subprocess import *
Popen("ds9 -title foo", shell=True, cwd="C:\\Program Files\\ds9\\")

Logged In: YES 
user_id=344921

Which Windows version are you using?

Logged In: YES 
user_id=431773

I am using Windows 2000 Professional.

Logged In: YES 
user_id=344921

This happens because cmd.exe/command.com opens a window by
default. To get rid of this, we need to pass SW_HIDE to
startupinfo.wShowWindow. 

I've fixed this in revision 1.8 of subprocess.py and
revision 1.3 of _subprocess.py: When using shell=True,
SW_HIDE is now default.