When you install 32-bit CPython 'for the current user
only' on 64-bit Windows, the installation does not show
up in the Windows 'Add/Remove Programs' dialog (a.k.a.
'Programs and Features' dialog on Windows 7). It does
not show up there even for the current user.

I tested this CPython installation behaviour with the
following CPython versions:
  * 2.3.4 - works correctly
  * 2.5.4 - works correctly
  * 2.6.0 - works correctly
  * 2.6.2 - works correctly
  * 2.6.3 - does not work correctly
  * 2.6.4 - does not work correctly
  * 2.6.6 - does not work correctly
  * 2.7.6 - does not work correctly
  * 3.3.3 - does not work correctly
  * 3.3.5 - does not work correctly
  * 3.4.0 - does not work correctly

All this has been tested using one Windows 7 SP1 (x64)
machine and using only CPython 3.4.0 installation on
another.

Several related observations, indicating that this could
be some sort of a Windows Installer misconfiguration
issue possibly solvable in the CPython installer:

* The same does not occur when you install a 64-bit
  CPython version - its entry is correctly displayed in
  the 'Add/Remove Programs' dialog.

* 32-bit CPython installer still correctly detects that a
  specific 32-bit version has already been installed,
  even if that previous installation is not listed in the
  'Add/Remove Programs' dialog.

* When you ask Windows using its WMI interface to list
  all the products installed on it (e.g. by running
  'wmic product list' on the command-line), all the
  installed CPython versions are correctly displayed,
  even the 32-bit versions not displayed in the
  'Add/Remove Programs' dialog.

I compared MSI packaging related CPython source code
(Tools/msi folder) in 2.6.2 & 2.6.3 releases but failed to
see anything suspicious there. It could be that the
observed beaviour change between those two versions is a
result of the final release packager changing his used
Windows Installer version, but I have not rebuilt CPython,
and its MSI installer to test this theory out.