Do not mix Office 32-bit and Office 64-bit
Excel kept saying that my .xlsx files weren't associated with Excel by default, so I thought to be clever and execute an
Office repair action:
- Control Panel > Programs > Programs & Features
- Microsoft Office 365 - en-us: right-click and choose "Change"
- Then you get the choice "Quick Repair" or "Online Repair"
I don't know what choice I made, but what I know, is that my Office installation was completely unusable because:
So, after that, I kep Microsoft SharePoint Designer 2010 - for my much beloved
Picture Manager, and I installed the 64-bit version of Microsoft Office as well.
Case closed!