After Windows 8.1 had performed an unscheduled reboot, I was greeted with the following error message when trying to start up a virtual machine in VMware Player:

This virtual machine appears to be in use.
If this virtual machine is not in use, press the “Take Ownership” button to obtain ownership of it. Otherwise, press the “Cancel” button to avoid damaging it.

I usually prefer VirtualBox for my non-commercial virtualization needs, but since I already had VMware Player 6.0.2 installed on a Windows 8.1 64-bit host I decided go with it for my Slackware Linux 64-bit guest.