Reading - who remain in the bottom three - made a fantastic start against their high-flying opponents as they took third minute lead through a Jason Donnelly penalty, before good support play from a lineout allowed Dan Witko to crash over for a converted score.
However Windsor hit back straight from the kick off, and after Reading had knocked on, talented centre Pat Birch went over to reduce the arrears.
Full-back Chris Laidler added the conversion and Birch then set up a try for wing Ben Anderton.
A drop goal from Laidler made the score 15-10 and it remained that way until the break, although Reading lost Stuart Borthwick to the sinbin.
Yet two minutes into the second half Reading were in front as a fine team move was finished off by Alex Murray-Smith.
Donnelly missed what should have been a straight forward conversion but his later penalty made it 18-15.
However, there was again a late twist as Reading were penalised on their own defensive five metre scrum and a tap penalty resulted in Birch going over for a try.
Reading visit Bletchley this coming Saturday (2.15pm).
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