hi,
if ever you tried any freeware alternative to get a "thumbnail tool tip" (I call it this way to avoid confusion with the name of the two existing freeware "visual task tips" & "visual tool tip"), and then uninstall these freewares ,
then if you install after window fx, the "thumbnail tool tip" is definitely broken ...
The thumbnail doesn't apppear anymore.
I guess these utilities are leaving registry entry that are fooling window fx.
This is just to make you aware of this problem ...