See the title!
It is stated on the web site that it runs on Windows 7, 8 and 10, but it is not specifically mentioned that it no longer runs on XP, except in the announcement on this forum. I guess they could list all the obsolete or unsupported versions of Windows where it will not work.
Fortunately there is a 100% money back guarantee, so write to eM Client, [email protected], and they will sort this out for you.