Hey guys,
So we're going to buy the 7 Day Travel Card for Zones 1 and 2 in London.
Yes, you can purchase the 7 day Travelcard at a tube station, but it will be loaded onto a plastic Oyster electronic card.
You can then add money to the same Oyster card to cover your journey from Heathrow. Tell the person at the Heathrow ticket office that you want to do a pay-as-you-go journey into town, and have a 7 day Travelcard for zone 1-2.
Windsor is completely outside the London fare system. Whatever you do for your Travelcard, you will have to purchase a separate ticket to travel from central London to Windsor and back. It's not far enough away to qualify for advance booking so simply buy a ticket on the day at Paddington, from where the fastest route to Windsor departs.
Thank you so much, Phillip! I'm going to print this so that in my jet lagged state, I will make sense at the ticket counter. ; )
Going to Windsor you can buy an extension ticket from the boundary of zone 2 to Windsor rather than a fresh ticket. May save a little.