What is needed is separate quoting for the command and the argument. 
Right now, test_popen only surrounds the entire command line with quotes:

"c:\Program Files\Python2.6\Python.exe -u c:\Documents and Settings\Russ
Gibson\cgi-bin\cgi.py"

It needs to the above as thus:

"c:\Program Files\Python2.6\Python.exe" -u "c:\Documents and
Settings\Russ Gibson\cgi-bin\cgi.py"

From the command line, the second case works, but the first doesn't. 
Neither work from os.popen in 2.6.2.

To make sure that popen works in all cases under windows, test_popen*
need to test with separate quotes around the command and argument.  That
will show the real problem with the current os.popen* implementation(s).

(yeah, I know, shut up and provide a patch...)