Cannot reinstall PostgreSQL because Windows thinks it's still installed - postgresql

Question

I've installed PostgreSQL but I want to reinstall it to another directory. So I've uninstalled it and when I execute the installer I get:
An existing PostgreSQL installation has been found at C:\Program Files (x86)\PostgreSQL\9.1. This installation will be upgraded.
I'll add that I didn't uninstall PostgreSQL with Add/Remove programs from Control Panel because I was getting an error in French so I just removed the main directory and then removed it from Control Panel.
I've also removed HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\postgresql-9.1 and WampServer which used PostgreSQL (just in case). I cannot find any other keys in regedit because the search is taking forever (and I think it's bugged). And I got rid of the directories C:\Users\<username>\AppData\Roaming\postgresql and C:\USers\postgresql.
Perhaps it has something to do with Visual Studio because when I run the installer I briefly get a window:

Answer 1

I've finally done it. I had to remove all keys in the Registry.
Seems obvious, right?
But Win10 Regedit is bugged and if there are keys that are longer than 255 chars it goes into an infinite loop. I've found no fix for this.
So one of the solutions is to download Regscanner, search for "postgre" and "pgadmin" and remove all entries but with Regedit. I mean, you can probably use Regscanner too but I prefered to delete keys with a native tool. It's a lot slower, though, as you have to manually find all keys.

Answer 2

Even though this already has a solution, I'm documenting the steps I had to take to accomplish a full manual uninstall on Windows Server 2016:
open a CMD window with "Run as Administrator"
sc query postgresql-9.1 or sc query postgresql-x64-9.1, use this for step 3 and 4.
if the STATE was RUNNING, then do: sc stop postgresql-9.1
sc delete postgresql-9.1
using the file explorer, locate the postgres software directory, probably "c:\Program Files (x86)\PostgreSQL\" ... right click on this, properties, security, ownership, take ownership, ok ok ok. then delete this folder and everything in it.
using the file explorer, locate the postgres data directory. Sometimes it's in the same directory as in step 5, and other times it will be in something like D:\postgres\data
net user postgres /delete
windows key + r to open Run prompt. Type regedit
scroll to HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node and/or HKEY_LOCAL_MACHINE\SOFTWARE
delete both folders with the word PostgreSQL in them