I thought I did something to Windows so I tried migrating back to a month old backup. But then I fought with macOS Sierra’s optimzed storage. Luckily, this free/unfree space issue seemingly was resolved after updating to 10.12.1.

So with space available, I tried working with an older copy of my VM to no luck. Still slow. Then I found this forum post describing a common problem with the combination of Sierra, Win10, and Parallels Desktop 12. None of the recommended fixes helped.

I tried downgrading to Parallels Desktop 11 but still slow. I even moved products, trying out VirtualBox and copying the .hds file from my Parallel’s VM file. With Gary’s help and his supercharged MacBook Pro, he encountered the same slowdown so it wasn’t just me and my MacBook Air. He did notice that my VM was woefully out of space, so he created another disk image and cloned content to it.

Then I found the Windows reset feature.  This nuclear option begins Windows 10 like it was brand new (but with data files retained). This had the biggest effect. The VM started behaving “like normal.” For me, having a functioning OS is a worth lost apps, but that’s fixable since I only have a handful of app to re-install.

I did move back to Parallels though due to Windows activation. Using VirtualBox deactivated my Windows with the underlying (virtualized) hardware changes. But back in Parallels, Windows was still activated. I even learned to link a Microsoft account to Windows 10 to store my Windows 10 digital activation information.

I’m hoping this ordeal with Windows is over…