Keith, if you can find a strawberry with light beige to golden brown seeds that are standing out from the skin of the berry, those seeds might be viable.
The one in your picture, I think was picked too early for the seeds to have matured. Leaving it on the windowsill won't really "ripen" the fruit much more than it already is, because it needs to stay attached to the plant to gain more sugar from the leaves and to help mature the seeds, too. Better eat it up!
I did it once (inadvertently) years ago with a strawberry that was hidden on a plant in my garden. By the time I found it the berry was drying out but the seeds were roughly 4 times the size of those on your strawberry, and as I said, sort of a golden brown color. I was able to scrape them off the berry quite easily, and they did germinate for me.
