Did you download the latest version? I changed the link in the first post. I'm 100% sure i checked .NET 4.0 Client Profile as target framework.
Also please check the XIM-Joystick.NET.exe.config file with an editor and try changing the version number from 4.5 to 4.0.
EDIT: OK I also changed the file again, try redownloading. Hope this finally works with XP, all my PCs have Win 7 or 8.