SUMMARY:

'Microsoft' is the platform.system() of Vista Windows, whereas 'Windows' 
was the platform.system() of XP Windows, whoops.

STEPS TO REPRODUCE & ACTUAL RESULTS:

Run 2.5.1 Python in a Vista and see:

>>> import platform
>>> platform.system()
>>>
'Microsoft'
>>> 

EXPECTED RESULTS:

>>> import platform
>>> platform.system()
'Windows'
>>> 

WORKAROUND:

Write new Python source code like:

if platform.system() in ('Windows', 'Microsoft'): 
if not (platform.system() in ('Windows', 'Microsoft')): 

in place of obsolete Python source code like:

if platform.system() == 'Windows': # Microsoft 
if platform.system() != 'Windows': # Microsoft 

REGRESSION/ ISOLATION:

Seen by me in an Enterprise Vista. Indexed by Google as reported by 
Martin v. Löwis (loewis) circa 2007-05-29 07:11 as:

http://mail.python.org/pipermail/patches/2007-June/022947.html 
... 

Patches item #1726668, was opened at 2007-05-28 03:23 

On Microsoft Vista platform.system() returns 'Microsoft' and 
platform.release() returns 'Windows' 

Under Microsoft Windows XP SP2 platform.system() returns 'Windows' and 
platform.release() returns 'XP'. 

This is problem was caused by a change in the output of the "ver" 
command. In Windows XP SP2 "ver" outputted 'Microsoft Windows XP 
[Version 5.1.2600]'  In Microsoft Vista "ver" outputted 'Microsoft 
Windows [Version 6.0.6000]'. The lack of the 3rd word before version 
causes _syscmd_ver(...) in platform.py to return 'Microsoft' for system 
instead of 'Microsoft Windows'. This causes uname() to return the 
incorrect values. Both system() and release() call uname().

NOTES:

There is no fixing all of this?

Cross-platform scripts actually will misbehave across the large 
population that is 2.5 Python in Vista unless those scripts change to 
implement something like the suggested workaround, that's now an 
accomplished fact.

Question: Is it better to leave this feature as is, so that everyone 
eventually learns to workaround it, or is it better to fix it late now 
in 2007-09, so that many people never have to learn to workaround it?

Question: Why are we screen-scraping the Ver command, instead of calling 
Win kernel32.getVersionEx? And how can any code for screen-scraping the 
Ver command be in doubt about whether the platform.system underneath is 
'Windows'?