Windows installer fails on Python 2.3 "Non-admin" install

[mboersma]

On Windows, run the python 2.3 binary installer, choosing
the "Advanced Options" button and specifying a "Non-admin
install".
After python's install completes, run the Twisted 1.0.7
python 2.3 windows installer (with or without docs, makes no
difference).
The installer then copies files to the mythical "ACK"
directory, failing at the end when it tries to exec
ACK\pythonw.exe.
The difference seems to be that the installer expects to
find certain registry keys under the HKLM hive, but in a
"Non-admin" install, those same keys are placed only under
HKEY_CURRENT_USER.  Checking first one, then the other,
should fix this.

[moonfallen]

Workaround, as noted by the mboersma on twisted-python, as
follows:

Prior to installing:
1. Launch regedit (Start>Run...>"regedit")
2. Navigate to HKEY_LOCAL_MACHINE\Software

If the Python key is missing, create the following keys
(Edit>New>Key, once for each of the following):
Python\PythonCore\2.3\InstallPath

3. Change the <default> key to the path where Python 2.3 is
installed, usually C:\python23

4. Run the Twisted installer as usual.

[moonfallen]

The 1.0.8alpha2 installer which I will build on Monday will
be the first release with this fix.

Attaching the diff so I can apply it to the tag on Monday.