J’ai reason to believe that I may have malware on my system in the form of an Explorer extension. I suspect this because Procmon shows that Explorer.exe keeps re-writing a certain Registry key that is intended to run a certain EXE au démarrage.
Comment find out what Explorer extensions are installed, and how do I remove them?
My personal favorite is Autoruns from Sysinternals (Microsoft). It goes well beyond just shell extensions and covers tons of areas where third party code can run.
Assuming you’ve done a virus scan and it didn’t catch it, you might want to watch this excellent video from Mark Russinovich on advanced malware cleaning techniques.