They were installed overnight to afford extra protection at Wednesday's Changing of the Guard ceremony in the wake of last week's attack in Westminster.
Police asked the public to understand why the barriers were "necessary".
But some residents in the Royal Borough have reacted angrily to the "over-the-top" measure.
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Many complained they were unsightly, while others said the number of parking spaces had been reduced as a result.
Shami Kalra said it was "sad"  to see the "beautiful streets of Windsor" lined with anti-terrorism barriers, and gave the impression the town was "running scared".
One woman living in the town said the "ugly barriers" had been installed with "two hours notice" and tweeted: "If it's not safe to change the guard. Don't do it. The barriers severely impact people who live there."
Thames Valley Police have said the measures were proportionate and necessary but that there was "no intelligence to indicate a specific threat to Windsor".
The barriers will be in addition to the normal road closures which had already been arranged for the Changing of the Guard event.
by Peter Cooke, BBC South Home Affairs correspondent
The police and security services face a constant balancing act of doing all they can to protect the public from acts of terror - whilst at the same time trying to maintain our civil liberties so we can continue to live in a free and open society.
No security infrastructure can ever remove all the risks. But the new barriers in Windsor are effective methods to stop vehicle attacks and to protect public spaces.
However some of these in-your-face barriers aren't always popular with the public.
But as we continue to face this low-tech and lone wolf form of terrorism it's likely we'll also see more obvious security measures being put in place at public spaces around the country.
From next month the colourful military spectacle will be held every Monday, Wednesday, Friday and Saturday.
Soldiers proceed to and from the historic building to the sound of a military band.
Roads will remain open at other times.
New security barriers around Windsor Castle have been branded "ugly" by some locals.