the installer went 2/3 through the process and was installing
already something in the default dir c:\Python34
Then after a small pause the error message was shown
and the installer removed all the files leaving an empty 
..\lib in the default dir

The behavior is quite reproducible with *.msi 
for python 3.4.0 and 3.4.1
Its independent on whether the prior installation dir is removed
or not
It is not an issue of the antivirus software
(I am running win7 prof sp1 with the latest updates)
It is not clear from the process but I am convinced this happens 
when the installer tries to register python in the registry

It never happened with any of the prior python 3.0 to 3.3.5

For the own compiled version I can run python.exe of the 3.4.1
sources but haven tested whether its executing anything fine.
So it does not seem to be a problem of python3.4.x on 32bit