yWriter5 exists in two versions: 5.2.1.2 which is many years old, and works on Windows 2000, and yWriter5 beta 5.6.1.9 which is new, and identical to yWriter7.
I want to keep the old yWriter 5.2.1.2 around, and so I've created a separate page on my website for it:
From this point on, yWriter5 release version will match the content and features of yWriter6 and yWriter7, and will be regularly updated.
A reminder that yWriter5 is for Windows XP, yWriter6 is for Windows Vista, and yWriter7 is for Windows 7/8/10. Having said that, you can run yWriter5 or 6 on Windows 10 if you want, although anyone using double-byte character sets should absolutely be using yWriter7 for technical reasons I won't go into here.
Cheers
Simon