identifying 64-bit Windows from 2.3.5?

[Steven Knight]

If I have installed 2.3.5 from the python.org Windows installer, can
any one point me to a run-time way to identify whether I'm running on
a 32-bit vs. 64-bit version of Windows XP, given that Python itself was
built on/for a 32-bit system?

I hoped sys.getwindowsversion() was the answer, but it returns the same
platform value (2) on both 32-bit and 64-bit systems.  sys.platform
("win32") and sys.maxint are both set at compile time.  Things like
os.uname() aren't on Windows.

Can some Windows-savvy Pythonista point me to some way to distinguish
between these two?

Thanks,

         --SK