This issue can confuse a regular user in the following
scenario:

1. User uses 'for current user only' Python installations.

2. User expects to be able to see all installed software
   listed in the 'Add/Remove Programs' dialog and does
   not know that the listing presented there might be
   incomplete, how to use WMI to get an alternative
   listing or have any other indication that he should
   look for some external software providing this
   listing.

3. User has 32-bit & 64-bit CPython 3.4.0rc3 installed on
   his machine.

4. User uninstalls the 64-bit CPython 3.4.0rc3 version
   and installs a new 64-bit CPython 3.4.0 release. No
   problems there.

5. User now wants to remove the old 32-bit CPython
   3.4.0rc3 installation from his computer.

6. User checks the 'Add/Remove Programs' dialog and does
   not see the installation listed there.

7. User checks the 32-bit CPython 3.4 related Start menu
   folder for an uninstall link, but all the links there are
   related only to the 64-bit CPython 3.4.0 installation.

8. User checks the 32-bit CPython 3.4.0rc3 installation
   target folder (where its python.exe and other files are
   located) but finds no uninstaller there either.

9. Since there is no uninstaller to be found for this CPython
   installation, user assumes it is ok to just delete its
   folder and does so.

10. User attempts to install a new 32-bit CPython 3.4.0
    installation and that breaks dues to not being able to
    uninstall a detected previous installation.

If user thinks of it - he can now work around this by finding
an old installation package for the previously installed
32-bit CPython version, running that, choosing to first
repair the current installation and then run the installation
again to remove the current installation.

Or clean up the previous installation's Windows Installer
related registry entries by hand (painful & error prone).

Or be unable to ever install a new version. :-)

And, speaking from personal experience :-D, if he does apply
the workaround he can 'feel dumb' about not locating and
trying out the original installation before removing the
original installed data and cuss & fuss about nothing around
him instructing him to look into that possibility. :-D

If nothing else, this could be 'patched up' by having
CPython's Windows installer that fails to uninstall a
previous installation, suggest manually repairing the
previous installation by running its installation package
directly before attempting to rerun this installation. It
could also reporting the original installation's install
package location on disk, as read from the registry
(Windows Installer makes a copy under some random generated
name which user is unlikely to find by simple trial & error).