Try this if you fail to (re)install Google Picasa on Windows

Today I lost quite some time figuring out why Google Picasa did not work correctly. Even though the latest version *was* installed already it proposed to download and install an update.

So the recommended way to fix Picasa issues is to uninstall and reinstall. Unfortunately the uninstall went fine, but it wouldn't reinstall. Even when every possible Picasa directory was (temporarily for the sake of hypothesis) removed. To no avail.