A DxDiag won't help.
It's been a long time (5 yrs or so) since I had to deactivate the game, so I might make some mistakes.
What you need to do is to use the activation code, which needs to be typed into the de-activation box. When that code is verified, you get a new code, which you'll need to type into a second box.
The reason for this is, that Securom needs to check if you are de-activating a legimite copy. Don't ask me why that is, I didn't come up with this system.
The activation codes can be found at the back of your manual, or - in case of digital download - at your game-list of the digital shop.
If uninstalling using the installation program itself isn't working, try using the uninstall-option found under task manager. You'll need to use the codes for that as well, but often that one does work.
And a request:
Please mind your language a bit. We all understand you're pretty fed up with the used system without seeing the censored swear-words you used.