I am in full agreement with Nergal
I have CCleaner v4.07.4369, and I am using a Windows 7 64-bit pc. I recently downloaded CC v4.07.4369 over the previous version of CC
That is NOT the correct terminology for the correct procedure, and it cannot happen that way.
You can download either the Portable ZIP or the Installer version of CC to a SEPARATE download folder, and then you are able to :-
Unzip the Portable version over the previous Portable version of CC; or
Install the Installer version over the previous version of CC.
If you really downloaded over the previous version of CC that would totally corrupt the old version,
and if you then unzipped/installed to the same place all settings would be trashed,
and starting the 32 bit version before handing over to the 64 bit version would be the least of your troubles,
and you really need to fully uninstall/remove the old and then download and start again properly.
I only use the portable version of CC,
and it is my experience that if I unzip both the 32 bit and 64 bit versions in the same folder,
then I can double click the 32 bit version and it immediately recognises that I have a 64 bit computer so it hands over immediately to the 64 bit version.
I have to rename CCleaner64.exe as CCleaner64.bin, or delete it, before I can use the 32 bit version to clean the 32 bit part of the system.
I do not think the Portable version is likely to have caused an error in the start-target.
If you used the Installer version then perhaps that has a bug and thought it was installing under a 32 bit system and so it fixed the start-target wrongly.