Well it may be uncommon, but it's perfectly easily reproducible:
Just try to reinstall / repair from a file not called 
python-2.5.2.msi. Maybe uninstall: haven't tried.
If Martin doesn't get there, I'll try to look at the log and 
see if there's something straightforward which can fix it.

Obviously, there's an easy workaround: rename the file
you're running to "python-2.5.2.msi". So I wouldn't consider
it a major priority. Just a nuisance.