To be clear, Player is only free for non-commercial use - those who use it in a commercial sense pay for their license.
So this is actually a Player vs Pro question, rather than a free vs paid question.
Not saying it’s a bad question, just adding that clarity.
Well, since to your host, a virtual machine is merely a set of files, you can ALWAYS make a point-in-time backup of your VM. Simply make sure it is powered off (and guest OS is shutdown, not just paused/suspended). Close out of Player. Use Windows Explorer to browse to the folder for the VM, and zip up the contents. I usually add the date to the name so I can keep multiple copies and easily know which was which.