Which came first, Harry Potter or Windows?

Windows came first, by 12 years. Microsoft shipped Windows 1.0.

Side by side

Harry Potter

Bloomsbury published the first book in June 1997 with a print run of 500 copies, most of which went to libraries, after twelve other publishers had rejected the manuscript. The company's chairman gave the first chapter to his eight-year-old daughter, who demanded the rest. It came out the same year as Netflix was founded and a year before Google.

Windows

Windows 1.0 shipped in November 1985, twenty-two months after the Macintosh, and it was not an operating system — it was a graphical shell running on top of MS-DOS, and remained so until Windows NT in 1993 and the consumer transition with Windows XP in 2001. Version 1.0 could not even overlap windows: they tiled, because Apple's legal position on overlapping windows was unresolved.