Microsoft discontinued support for Windows XP in 2014:
SeeYou is upgraded all the time with the latest features and software libraries. Due to the lack of Microsoft support for Windows XP some of these libraries do not work on XP any more which means that we had to stop supporting Windows XP starting with SeeYou version 8.3.
Earlier versions will still run but you will be missing all the new features.
If you would like to use SeeYou on Windows XP please write to firstname.lastname@example.org and we will be happy to help you.