Impossible to desinstall older versions of Adobe Digital Editions

Hello,

I am enable to transfer books from library (epub 3) to my Kobo reader, and I was told that I should delete the version 4 of Adobe Digital Editions (ADE) and to install rather Adobe Digital Editions 3.

After desinstalling version 4 and reinstalling the version 3, I cannot upload the book in ADE.

The software itself opens fine; the problem is when I try to retrieve the loan from the library. It's like an other version is still running somewhere in my computer.

After I desinstalled ADE 4 and installed ADE 3, when I click on "Retrieve your loan [Récupérez votre prêt]" in the email that I got from the library, it prompts a window:

"The installation program has detected a new version. Do you wish to repare the old version?"

If I click no, it says "The installation has stopped [Installation abandonnée]". 

If I click yes, then the same dialogue boxes of when I installed the software appear. But the book won't upload.

If I go back in the email I got from the library and click again on "Retrieve your loan", I get a message saying that "ADE is already running".

Here is what I did to delete ADE 4 and install ADE 3:

- I deleted the authorization of my computer in ADE.

- I went in my Settings, Applications, and right click on ADE to uninstall it.

- I went in the "Downloads" folder of my computer and deleted the ADE file.

- I went in My Documents, and deleted the folder My Digital Editions.

- I went in Démarrer -> Exécuter. I type in « regedit », and under Software, I deleted the whole folder HKEY_CURRENT_USER>Software>Adobe>Digital Editions and HKEY_CURRENT_USER>Software>Adobe>Adept.

- I emptied the waste basket.

- I ran the CCleaner software to do a Custom clean.

- I restarted my computer.

- Then, I downloaded ADE 3 and reauthorized my computer.

What did I do wrong? How can I ensure that all versions of ADE are completely deleted? Thanks in advance for any advice.