Unfortunately the parish records for Windsor, Berkshire are not available online which would be why you can't find the baptisms you need.
I note from the census that Pond's born Windsor in the same time frame are:
Joseph bc.1788
William b.1790
Thomas bc.1793
Francis bc.1795
Edward bc.1803
Unless someone is able to visit the Berkshire Record Office and check records there for you I would suggest you contact the record office directly.
I'm guessing that your Joseph Pond married Ann Brisoe 29/6/1813 St. Bridge, Fleet St., London (people living around London often married in London itself where they often went for work).
I note that Ann, his wife, was bc.1787 Stoke St. Milborough, Shropshire and there is a baptism for Ann Briscoe bp.18/3/1787 Stoke St. Milborough, Shropshire, dau. of John and Mary (on familysearch). You may well have this information already of course.
So, Berkshire Record Office hold the records you need.
Annette