subprocess.Popen fails, but os.system works

[bahoo]

Hi,

I am using Windows + Python 2.5.

This line of code fails (see error message at the end),

last_line = subprocess.Popen(["D:/release/win.exe 0.5 1000 100 D:/
images/img.ppm out.ppm"], stdout=subprocess.PIPE).communicate()[0]

but using "os.system" works:
os.system('D:/release/win.exe 0.5 1000 100 D:/images/img.ppm out.ppm')

----------
C:/Python25/pythonw.exe -u  "D:/run.pyw"
Traceback (most recent call last):
  File "D:/run.pyw", line 59, in <module>
    process_dir(mydir)
  File "D:/run.pyw", line 52, in process_dir
    segmentation (dir,f)
  File "D:/run.pyw", line 35, in segmentation
    last_line = subprocess.Popen(["D:/release/win.exe 0.5 1000 100 D:/
images/img.ppm out.ppm"], stdout=subprocess.PIPE).communicate()[0]
  File "C:\Python25\lib\subprocess.py", line 593, in __init__
    errread, errwrite)
  File "C:\Python25\lib\subprocess.py", line 793, in _execute_child
    startupinfo)
WindowsError: [Error 22] The filename, directory name, or volume label
syntax is incorrect
-----------

Can anyone tell me why?
Thanks
bahoo