Python-2.3.5.exe seems to be corrupt. I’ve tried downloading Python-2.3.5.exe a number of times in the past week, and so have a few of my colleagues. It always transfers in an incomplete manner, resulting in only 4.7 out of 9.1 MB. I have tried from several different Windows 7 boxes, with the same results. Perhaps something in my environment is messed up, but it may be that the file is corrupt on your server.
I tried to download it on a win xp machine and I succeeded at the first attempt (even thought it seemed to be stuck for a few seconds before reaching 100%). I was also able to start the installer, even thought I didn't install it. This is the version I downloaded: http://www.python.org/ftp/python/2.3.5/Python-2.3.5.exe May I ask you why you are attempting to download such an old release, and not even the latest 2.3 (there's 2.3.7 available, that also includes some security fixes)?