Do you mean this first column:
which looks like this in my setting? 
This is just the symbol of the default player software associated with your music format.
You can set it in your Windows OS to whatever (installed) player you like.
But as @ohrenkino said: The Windows version of Mp3tag has never had a real cover art preview in a column.
BTW: You can enable the Tag Panel on the left with Ctrl + Q.
And you can arrange it wherever you like it.