Uh, I was running iTunes on my Windows PCs to support my iPod, long before running it on a Mac. Early 2000's. iTunes will run on current PCs.
Also, I bet not on third party players? Unless you convert the song to mp3, which of course, is a new feature that Apple added to their ITunes software recently. Versus having to burn the song to a cd and then rip the cd back to an MP3 get it in MP3 format.
I do give Apple credit for dealing with the DRM issue and the media companies. After napster, everyone ran from the media companies yet Apple faced and successfully convinced them that there was money to be had if their songs and movies were sold legally. A LOT OF MONEY.