Install pgAdmin III on Windows 7 without administrator rights

Question

I'm trying to install pgAdmin III, using the v1.20.0 package from pgadmin.org. I found a few sources that suggest I should be able to install it for the current user only without having to provide the administrator password, but I haven't been able to get it to work.

This mailing list item says, of the v1.12.3 package:

We don't set any properties that should force a per-machine installation as far as I can see (we certainly don't force ALLUSERS on). You might try installing form the command line with a command like this:

msiexec /i pgadmin3.msi ALLUSERS=""

That should run the installer but for it into per-user mode.

In this StackOverflow question, the OP comments:

I used ALLUSERS=2 and MSIINTSTALLPERUSER=1

So, reading the linked pages in that Q&A (but only understanding some of what I was reading), I tried a few variations:

PS C:\Users\ath\Downloads\pgadmin3-1.20.0> msiexec /i pgadmin3.msi ALLUSERS=2
PS C:\Users\ath\Downloads\pgadmin3-1.20.0> msiexec /i pgadmin3.msi ALLUSERS=""
PS C:\Users\ath\Downloads\pgadmin3-1.20.0> msiexec /i pgadmin3.msi ALLUSERS="" MSIINSTALLPERUSER=1

In each case, the final "Install" button has an administrator shield icon and when I click it to proceed, the password dialog pops up; canceling out of the dialog halts the installation.

I'm not sure if I'm using msiexec wrong or if these workarounds simply don't work for this combination of software and OS versions.

How can I install pgAdmin III on Windows 7 without administrator rights? Is there any reason to believe this isn't possible, other than my failure so far?