Day driving trip out from Windsor, any suggestions?

I highly suggest Warwick Castle, its about 1hr and 15 min drive from Windsor. Its a fine example of a castle for teenage boys.

I can't imagine how you could see more than Highclere, Stonehenge, and perhaps Salisbury in a day trip from Windsor. Far too much to see in Bath to make it worthwhile to try in one day. Same for Blenheim and Warwick. If you had a second day, Oxford, Blenheim, Kenilworth, Stratford, Coventry, Warwick are possibilities.

Thank you the replies. I am a little leery of trying to bite off more than we can chew in a day but I do feel that a morning at Highclere and a stop at Stonehenge should leave several hours open in the afternoon but not enough time to tour Blenheim or Warwick. I think we could knock out Warwick with the allotted time but Im just a little concerned with the distance up to Warwick, driving back to LHR to return the car and a cab back to Windsor all before nightfall.My best guess it would leave us 2 to 3 hours at Warwick before driving back. That's why I was inquiring if there were some other smaller sights to see other than the drive north to Warwick or Blenheim. I guess we will keep Salisbury in our back pocket. I do love cathedrals. Old Sarum ruins look interesting.

Salisbury cathedral is wonderful. The close is a wonderful walk and the town is charming. Old Sarum is a complete ruin. It is fine for a few minutes and to contemplate the persons who trod the ground there.

What about stopping by Avebury? It's about 25 miles north of Stonehenge. You can actually wander through the stone circle there, unlike at Stonehenge. There's also a manor house that has been recently refurbished in five different styles to show how home decor has changed over time, as well as a archaeology museum and some other prehistoric sites. Info on Avebury can be found in Rick's England or Britain books. Or for something more nautical, you can check out the Historic Dockyard at Portsmouth, on the coast about 50 miles SE of Stonehenge. They should be opening a brand-new museum soon about the Tudor warship the Mary Rose, which sunk in 1545 and was raised in 1982. You can also tour Lord Nelson's ship the HMS Victory, which won the 1805 Battle of Trafalgar. Portsmouth is just covered by Rick's England book. I assume you're Downton Abbey fans if you're going to Highclere Castle. I was there last summer and it was great (although pouring rain kept us out of the gardens). Warning, it gets very packed with tour groups and there was a several hour wait to see the Egyptian artifacts in the basement, so we skipped them. I would advise buying your Highclere tickets ASAP if you have not already done so and ask when you get there whether you can see the Egyptian stuff first.

You might enjoy adding Winchester. The interior of the cathedral is very intriguing, and it's interesting to compare it with Salisbury. Winchester is also a pleasant town for strolling and for dinner. You can see King Arthur's round table (actually it dates from the 1300's) on display.....I would suggest visiting Stonehenge either as early in the day as possible or late in the day. You might want to look into signing up for private access to Stonehenge. This allows you to actually enter the circle. It costs extra to do this and visits are either very early morning or in the evening after closing. If you want to do that, you need to make the arrangements ASAP.

Thanks Lauren and Cynthia for the great advise! I love anything to to with Tudors, Nelson and his navy! Winchester? I take it is a cathedral? You both have given me good research to do this weekend. Yes we are Downton fans & we know we need to decide rather quickly. Right now there is still availability in July to tour both morn or afternoon slots.
Thank you all!

If you are at Stonehenge, to me the obvious choices are Avebury and /or Salisbury Cathedral and Close. (depending on time available). Keep Blenheim in your back pocket as it is on the way back to Windsor, but you probably need most of an afternoon to do it properly. Another choice with flexibility is to do the thames river villages and towns- Henley and Richmond,(and Richmond park). I just cant see that you need 9or will have time for) the extra travel time to Winchester or Warwick or Bath