Finally got the email. Installed it, ran the main stuff, it asked me to reboot to finish the process. I did.
Upon reboot, the screen showed System Mechanic was making "repairs" to my C Drive.
Then, it rebooted again, only to see the Windows 8.1 repair screen. It said I needed to use startup repair, so I did. It failed.
OK, so it offered me system restore, which I opted for.
Thankfully, system restore removed System Mechanic and all is well.
Either the new System Mechanic isn't ready for Windows 8.1, or not ready for dual boot systems, or SSDs or something. It sure did mess with my system.
But it's gone now.
I'd set a restore point before trying this software. Word to the wise!