I fail to reproduce the issue on Windows 7 (Version 6.0.1, number 7601, Service Pack 1):
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Microsoft Windows [version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. Tous droits réservés.

C:\Users\haypo>cd \python33

C:\Python33>python.exe
Python 3.3.0rc2 (v3.3.0rc2:88a0792e8ba3, Sep  9 2012, 10:13:38) [MSC v.1600 64 b
it (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()

C:\Python33>python.exe -m test test_buffer test_lzma
[1/2] test_buffer
[2/2] test_lzma
All 2 tests OK.
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I'm running Windows 7 in KVM, my host CPU is a Intel i7-2600.

> I'm getting these failures in test_buffer, 
> but I can *not* reproduce them when I build
> Win-32/pgo/python.exe from source:

The issue looks to be specific to 64 bits binaries. You need the professional version of Visual Studio 10. The express version doesn't support 64 bits. I only have the Express version.